Anatomical diagrams of the ewe : a key to the large chart of a pregnant ewe, with explanatory notes

Wilkie, Henry C. (Henry Charles), Govt. Printer, Wellington, N.Z., 1904

This eBook is a reproduction produced by the National Library of New Zealand from source material that we believe has no known copyright. Additional physical and digital editions are available from the National Library of New Zealand.

EPUB ISBN: 978-0-908329-82-3

PDF ISBN: 978-0-908332-78-6

The original publication details are as follows:

Title: Anatomical diagrams of the ewe : a key to the large chart of a pregnant ewe, with explanatory notes

Author: Wilkie, Henry C. (Henry Charles)

Published: Govt. Printer, Wellington, N.Z., 1904

ANATOMICAL DIAGRAMS OF THE EWE.

A KEY TO THE LARGE CHART OF A PREGNANT EWE,

WITH EXPLANATORY NOTES,

BY HENRY C. WILKIE, F.K.C.V.S.. VETERINARY DIVISION. DEPARTMENT ()| AdUICI [.TURK. NKW / !•; AI >A Mi,

WELLINGTON

1-tV AUTHORITY: JOHN MACKAV. GOVERNMENT PRINTED

1904

ANATOMICAL DIAGRAMS OF THE EWE.

PREFACE.

p 1 VERY ONE who has undertaken the task of teaching the rudiments of veterinary anatomy to students, or the delivery of lectures on first-aid to farmers, has no doubt felt the want of large anatomical diagrams for use in the lecture-hall. I have attempted to supply some of the most commonly needed of these by a series of drawings, some in colours and some in black-and-white, of which the sectional diagram of the ewe is, perhaps, the most elaborated.

Phis has been built up from a large number of dissections which I made for the purpose, such parts as the foetal envelopes, the p/acentu/ee, the bladder, &c., which do not lend themselves to direct representation, being rendered purely diagrammatically for the sake of clearness.

The original drawing, which was lithographed without reduction, measures 50 in. by 36 in., the figure being the natural size of a moderately large ewe.

In the key to this diagram I have made special drawings of the head, the thorax, and the lamb as it ties in the uterus immediately before birth.

In preparing the letterpress I have aimed at giving such a concise description of all the principal parts represented as will enable any one unacquainted with anatomy to gain a correct idea of their uses in the economy.

The technical terms used are explained by their derivations, as 1 believe even a casual inquiry into the origin of anatomical terms in common use is sufficient not only to arouse much interest in the student, but to impress the position of parts and the names of parts indelibly upon his memory.

H. C. W

Dunedin, New Zealand, 14th May, 1904

CONTENTS.

Fig. 1. A Longitudinal, Section of the Pregnant Ewe.

Fig. 2. The Head.

Fig 3. The Thorax.

Fig. 4 The Fœtus in utero.

FIG- I.

LONGITUDINAL SECTION OF THE PREGNANT EWE.

[Drawn by H. C. Wilkie

Entered at Stationers’ Hall, 1903.j

REFERENCES TO FIG. I.

1. One of the fasciculi of the trausversalis colli, a muscle which covers the sides of the last five bones of the neck —the cervical vertebra?. The action of this muscle is to extend and

flex, or bend, the neck. 2, 3. Two of the six intertransversales muscles, the action of which is to bend the neck sideways.

4. A fasciculus of the trausversalis colli muscle

5. The middle portion of the ligamentum undue, a ligament which is the chief support of the head in quadrupeds. The analogue of this ligament in man is a thin fibrous baud extending from the tubercle and spine of the occiput to the spinous process of the seventh cervical vertebra. In the sheep the ligamentum uuchse has a specially strong white middle portion, as here represented.

6. The superior spinous process of the seventh cervical vertebra. This bone is distinguished by the name of prominens, which it better deserves in the sheep and the ox than in the horse, in which animal the process is relatively very much smaller.

7. The longus colli muscle, which is attached to the under-surface of all the bones of the neck and the first six bones in the hack. Its action is to bend the neck.

8, The superior spinous process of the first dorsal vertebra

9. Skin

10. The common super spinous ligament, which extends to the sacrum or roof of the pelvis.

11. One of the fasciculi of the transverse spinous muscles, which is continuous with the trausversalis colli. It is an extensor of

the spine. 12. A facet for articulation with the head of a nb. In the tormation of these Facets two vertebne take part, as is seen m

the diagram. 13 A facet for the reception of the tubercle of a rib. 14 An intervertebral cartilage. This is a thick fibrous cartilage

interposed between the bodies ot the vertebrae

m—;*■>»«• Ligamentum. —Latin, ligo , I bind. Nuchas. —Latin, wucfca, of the nape neok. Occiput. —Latin, occiput, the back part of the head. FA°c E 8 T A " French: “’AmalHaco, a smooth circumscribed surface. ; EngliBh ’ Vertebra ’’ b6tWeen the VortebrfP ' Cartilage. —Latin, cciYtilago, gristle.

15. A branch of the great vena azygos described under Fig. 11l

16. A portion of the longissimus dorsi, the most powerful muscle of

the body. This muscle is cut in front to show underlying structures, and also at the side. It is mainly an extensor of the spine, or when one muscle acts singly it bends the body to the side.

17. The right kidney. The kidneys are organs which secrete urea and other waste products from the system, and are situated in the lumbar region behind the peritoneum. They are not lobulated in the sheep as in the ox, and are situated in a mass of fat which extends from behind the twelfth rib to the transverse process of the fifth lumbar vertebra.

18. Fat

19. Cut surface of the renal or kidney fat

20. The ureter, a tube which conveys the urine from the kidney to the bladder.

21. The great psoas muscle. This muscle is attached to the bodies of the two last dorsal and the lumbar vertebne, under the transverse processes of which it is seen to be lying in the diagram. Its posterior attachment is to a process on the femur (the internal trochanter). Its action is to bend the thigh and turn it outwards, or w r hen the thigh is a fixed point it bends the loins.

22. The posterior vena cava. Described under Fig. 11l

23. The abdominal or posterior aorta. Described under Fig. 11l

24. Cut bone. This is a portion of the pelvis, the ilium.

25. Cut section of the gluteus externus muscle, an extensor and a rotator of the thigh.

26. Cut section of the gluteus internus, or deep gluteal muscle. This is an abductor of the thigh.

Longissimus. —Latin, longissimus, very long. Dobsi. —Latin, dorsi, of the back. Kidney. - Old English, kidnere, or kidnei. Lumbar. —Latin, lumbus, the loin. Peritoneum. —A serous membrane which lines the whole ot the abdomen, and is stretched over or envelopes more or less completely the contained viscera. The kidneys, however, are behind the peritoneum. Greek, peritonaion, that which is stretched over— peri, around; tenio, I stretch. Renal. —Latin, renes, the kidneys. Ureter. —Greek, oureter. One of the passages through which the urine flows from the kidneys to the bladder. Psoas. —Greek, psoa, the loins. Femur. —Latin, femur, the thigh. Trochanter. —Greek, trochao, I roll round. Pelvis. —Latin, pelvis, a basin. Ilium. —A bone which forms the major part of the pelvis. Latin, ilia, the flanks. Gluteus. —Greek, gloutos, the hip. Abductor.— Latin, abductor, that which draws outwards.

.27. Cut section of the gluteus maximus, or middle gluteal muscle. This muscle extends the thigh, or, when the thigh is a fixed point, assists in raising the body, as in rearing.

28. The rectum, the posterior portion of the digestive canal. Its mode of attachment is here seen in the semi-transparent folds of the meso-rectum.

29. The bladder, the reservoir for the urine, is thin and of great capacity as in all ruminants.

At the closed end of this organ a small blunt point is seen, on which there is a cicatrix. This scar is caused by the obliteration of the urachus, a tube which, before birth, conveys the urine of the lamb into the sac of the allantois, as described under Fig. IV.

30. A fasciculus of the erector coccygis, a muscle which raises the tail

31. A portion of the compressor coccygis, a muscle which depresses the whole tail.

32. A fasciculus of the curvator coccygis which bends the tail sidewavs.

33. A fasciculus of the depressor coccygis which bends the tail downwards.

3-1. Shows the entrance of one of the ureters into the bladder. The ureters do not enter directly into the bladder, but they first penetrate the muscular coat of the organ, and then lie for a little distance between this and the inner coat or mucous membrane before opening into the cavity of the viscus. In this way any flowing-back of the urine into the ureter is prevented.

35. The vagina.

36. The meatus urinarius, or opening of the urethra, showing the small valve surmounting a eul-de-sac on the floor of the passage.

37. The clitoris

38. Bone, the floor of the pelvis.

89. One of the kidney-shaped lymphatic glands of the udder

40. The gracilis —a muscle which is an adductor of the limb.

Rectum. — Latin, rectus, straight. Meso-bectum. —Greek, mesos , middle. A fold of peritoneum which supports the rectum from the front of the sacrum. Cicatrix. —Latin, cicatrix, a soar. Urachus. —Greek, ouron, urine ; echo, I hold. Coccyqis.— Latin, coccyx, the cuckoo—so named from the resemblance of the four terminal bones of the spinal column in man to the beak of the cuckoo. Vagina. —Latin, vagina, a sheath. Clitoris. —Gre. k, kleitoris : from kleio, I shut. Lymphatic Glands. —The lymphatic or absorbent vessels, which convey waste material from the tissues to the blood-stream by way of the thoracic duct (as described under Fig. III.), pass in their course through certain rounded bodies, the lymphatic glands. In their passage through these the lymph has corpuscles added to it which afterwards become white blood-corpuscles. Latin, lympha, water; glans, an acorn. Gracilis. —Latin, gracilis, slender. This muscle is so named on account of its flat thin conformation. Adductor. —Latin, adductor, that which draws inwards.

41. The mammary artery

42. The mammary vein.

13. The semimembranosus muscle, or great ischio-femoralis. ihis is an adductor of the limb and an extensor of the thigh. When the thigh is a fixed point it raises the body, as in rearing.

44. The semitendinosus muscle, or ischio-tibialis medius. I bis is a flexor of the limb, and when the thigh is a fixed point its action is similar to that of the preceding muscle.

45. The gastrocnemius externns muscle, whose tendon is fixed upon the point of the hock. It extends the foot upon the leg.

16. The oblique flexor of the phalanges. The tendon of this muscle becomes united to the perforans tendon below.

47. The flexor pedis perforans, the tendon of which bifurcates opposite the fetlock-joint, the branches being ultimately attached to the third phalange of each digit. It is a flexor of the limb.

48. The tendon of the gastrocnemius interims muscle which turns round the tendon of the externns above the joint from the inside, and passes over the point of the hock, where it is widened to form a cap. It then extends down the back of the limb as the perforatus tendon.

49. The external superficial ligament of the hock. 50. The perforatus tendon bifurcates at the fetlock-joint to form two branches —an internal and an external. These branches pass down behind the two branches of the perforans and become attached to the upper and posterior part of the second phalange. Before reaching their attachment each branch bifurcates to allow of the passage of the underlying branch of the perforans.

51. The perforans. This tendon bifurcates just above the fetlock, each branch passing down behind a digit. These two branches, after passing through the two branches of the perforates, reach the inferior surface of each third phalange, where thev become blended with the plantar cushion.

52. The superior suspensory ligament of the fetlock

53. The capsular ligament of the fetlock-joint

54. A reinforcing ligamentous band.

55. The foot. The foot of the sheep consists of two digits, each covered with a horny claw. The heel of the claw consists of elastic rubber-like horn which immediately covers a laro-e • b

Mammary. —Latin, mamma, the breast. Semimembranosus.— Latin, semi, half; membrana, membrane. Semitendinosus. —Latin, semi, half; tendo, I stretch : half-tendinous. Gastrocnemius. —Greek, gaster, the belly ; kneme, the leg. So named from these muscles forming the calf or belly of the leg in man. Phalanges. The bones of the fingers or toes. Greek, phalangx, a line of battle, Pedis. —Latin, pes, a foot.

pad called the plantar cushion. The union of the claw and the underlying structures is, on the wall, by means of lamina, and, on the sole, by papillte, as in the foot of the horse. The leaves or laminae are, however, finer and much more numerous in the sheep than in equine animals. Behind and above each claw is a small horny growth called th e ergot.

p6. Ihe interungulate gland is a long pouch formed by an inversion ol the skin. Its blind end is firmly attached behind the digits at the bifurcation of the perforans tendon. It passes forwards between the digits and terminates in a pointed extremity in front of the limb just below the fetlock-joint, where it is attached to the skin, in which it has a circular orifice. This pouch, which is also known as the sinus cutaneus angulartm , is lined with fine hairs and secretes a thick sebaceous matter. So far as the domesticated animals are concerned, it is peculiar to the sheep, and it appears to act the part of a pad or buffer between the claws.

57. The orifice of the interungulate gland.

58. The large metatarsal bone.

59. The extensor pedis tendon.

60. The extensor pedis muscle.

61. The galactophorous sinus, or milk-cistern. This is a reservoir in the udder for the collection and retention of the milk.

62. Orifice of one of the lactiferous ducts which convey the milk from the acini of the gland, where it is secreted, to the milk-cistern.

63. The teat of the ewe exhibits some characteristics which are found in all ovine animals. It is long, thin, and pointed, laterally placed on the ndder, and projects considerably forwards as well as downwards. Its walls are thin, and it has a distinct sphincter of circular muscular fibres around the single orifice of its free extremity, which is marked by a peculiar lip-like prominence.

64. A portion of the cut abdominal wall turned over in section

65. A portion of the cavity of the abdomen is seen here, the stomach and intestines having been removed.

Plantar. —Latin, plantaris, belonging to the sole of the foot. Laminae. — Latin, lamina, a thin plate or leaf. Papillae.—Latin, papilla, a pimple. Ergot. —French, ergut, a cock’s spur. Interunqulatf,.- Latin, inter, between ; uvgula, a hoof or claw Bifurcation. —Latin, bis, twice; furca, a fork. Sebaceous. —Containing fatty matter. Latin, sebum, tallow. Metatarsal. —Greek, meta, beyond; tarsus, the hook. Galactophorous. —Greek, gala, milk ; phoreo, I carry. Lactiferous. —Latin, lac, milk ; fero, 1 bear. « Sphincter, —Greek, sphingkter, that which contracts,

66 The liver. Most of the blood from the alimentary canal passes through the liver on its way back to the heart, and this organ secretes bile, produces glycogen (which is concerned in the production of muscular energy and heat), and in other ways changes the blood which passes through it.

67. A reinforcing ligamentous band.

68. The interungulate gland.

69. The capsular ligament of the fetlock-joint.

70. The perforatus tendon

71. The superior suspensory ligament of the fetlock

72. The large metacarpal bone

73. The perforans tendon.

74. The capsular ligament of the knee-joint

75. The flexor pedis perforatus muscle. This is composed of two portions in the sheep, whose tendons unite about midway between the knee and the fetlock.

76. The oblique flexor of the metacarpus.

77. The internal flexor of the metacarpus

78. The extensor metacarpi magnus muscle.

79. Cut portion of the transverse pectoral muscle.

80, Cat portion of the anterior pectoral muscle.

81. The external thoracic artery.

82. The axillary vein

83. The axil!ary artery.

84. The inferior cervical artery.

85. The suhscapular artery.

86. The carotid artery.

87. Cut end of the inferior portion of the scalenus muscle. With the rib as a fixed noint this muscle Hexes the neck to one side or the other, or if both muscles act together the neck is flexed directly downwards. If the neck is the fixed point the first rib is drawn forward, and thus this muscle aids in inspiration.

88. A large lymphatic gland —one of the prepectoral group.

89. The jugular rein.

90. The superior portion of the scalenus muscle.

91. The accessory jugular vein.

Liver. —Anglo-Saxon, lifere or lifer ; German, leber. Axillary. —Latin, axilla, the armpit. Sub&capular. —Latin, sub, under ; scapula, the shoulder-blade. Carotid. -Greek, karoo, 1 stupefy; deep sleep. From the idea the ancients had that deep sleep was produced by an increased flow of blood in these arteries. Scalenus. —Latin, scalenus, a triangle of unequal sides and angles. Jugular. —Latin, jngulum, the collar-bone. This vein was so named from its proximity to the collar bone. Prepectoral. —Latin, pre or prce, before ; pectoris, of the breast.

FIG. M.

LONGITUDINAL SECTION OF THE HEAD OF THE EWE.

Entered at Stationers’ Hall, 1904.]

i Drawn by H. C. Wilkie

REFERENCES TO FIG. 11.

1. The cerebrum, the principal portion of the brain, which consists of two hemispheres—here seen in section.

2. The vault of the cranium

3, The eustachian tube, opening into the pharynx. This is a cartilaginous canal which conveys the external air to the middle ear.

4. The cerebellum, or lower brain, showing the white substance enveloped on every side by the grey. This substance, ramifying from two nuclei, forms a tree-like figure which was formerly called the arbor vitae.

5. The occipital bone.

6. Skin

7. Muscle. The rectus capitis posticus minor, a small muscle which lies upon the occipito-atloid articulation, and assists in extending the head upon the neck.

8. The spinal cord as it emerges through the foramen magnum

9. The atlas, or first bone of the neck

10 The cordifonn portion of the ligamentum nucha. This powerful ligament, which is the main support of the head and neck in quadrupeds, consists of two portions, a cord-like one and a lamellar. The cordifonn portion extends directly from the cervical tuberosity of the occipital bone to the spinous process of the second dorsal vertebra, where it becomes continuous with the common superspinous ligament, and in this way extends right along the back to the sacrum, or that portion of the spinal column which forms a roof to the pelvis. The lamellar portion is a Hat triangular ligament which fills up the space between the last six dorsal vertebra;, its cordifonn portion,

Eustawii^nT—So Earned' Eustachius. who first described this CEREBBLLBM.-Latin, cerebellum, the lower or small brain. -LaUn, nucleus, a kernel; from nux, a nut. OcciPiTAL.-Latin, occiput, the back of the head. Rectus. —Latin, rectus, straight. Capitis.— Latin, caput, the head. Latin, posticus, behind.. £rom j bore The foramen magnum is a Foramen. Latin,/orawten, f vh i o h’allows of the passage of the spinal cord. large opening in the occiput j- bear Greek mythology the god ATL Mahore the r °earth upon his shoulders aJ the atlas, or first bone of the neck, bears ; fr back or upper part of the LAMELLAR.-Latin. lamella, a small plate : from lamina, a plate. Cervical. — Latin, cervix, the neck. Occipital. - Of the occiput • DOBSAL-Latm, dorsum, the back. Vertebra —Latin, verto I turn. Supebspinobs.— Above the spine.

and the spinous process of the second dorsal vertebra. In the sheep this part of the ligamentum nucha; shows a distinct arrangement of very strong white fibres, as is shown in Pi*. 1.

11. Muscle —the great oblique muscle of the head, the axoidoatloideus or obliquus capitis inferior. This is the special rotator of the head.

12. The lamellar portion of the ligamentum nucha

13. The axis, or second bone of the neck.

14. Muscle. This is a portion of the transversalis colli, a muscle which covers the sides of the last five cervical vertebra;. It is both an extensor and a flexor of the neck.

15. Muscle —the longus colli. This muscle is attached to the undersurface of all the cervical and the first six dorsal vertebra; That portion of it which enters the chest is seen in Pig. 1 It flexes the neck.

16. The larynx —the upper portion of the windpipe, specialised as the organ of voice.

17. The oesophagus, or gullet, the entrance to which is seen immediately above.

18. The inner surface of the windpipe or trachea, the outer half having been cut away.

19. The thyroid gland, named from its nearness to the thyroid cartilage —a shield-shaped body which forms most of the anterior wall of the larynx.

20. The external surface of the windpipe

21. The .sublingual salivary gland

22. Muscle —the great hyo-glossus. This muscle retracts the tongue.

23. Muscle —the genio-hyoideus. This muscle draws the os hyoides, or bone of the tongue, forwards and downwards.

24. The palatine bone, the bony basis of the palate

Axoido-atloideus.— Axis, the second bone of the neck ; alias, the first bone. Transvebsalis.— Latin, transversalis, lying across. Colli. —Latin, collum, the neck. Longus. - Latin, longus, long. . Larynx. -Greek, larungx, the upper part of the windpipe (Esophagus. -Greek, oisovhagus, the gullet: from ow , I boar ; phago, I eat. Trachea. Greek, tracheia, the windpipe. Thyroid —Greek, thureos , a shield ; eidos , a resemblance. Sublingual. —Under the tongue. Latin, lingua, the tongue. Salivary.— Secreting saliva Latin, saliva, the spittle. Hyo olossus -Hyo, from the Greek letter upsilon, the shape of the hyoid bone, a U-shaped bone between the tongue and the larynx ; Glossus- Greek, glcssa, a Gbnio^hyoiiybds. —Oenio signifies a connection with the jaw. Greek, gentian, the chin. Os. -Latin, os, a bone. Palatine. — Latin, palatus, the palate,

25. Muscle—the yenio-gloss us. The action of this muscle is much diversified, as it can bring the tongue forward, draw it downward to the floor of the mouth, or carry it upward into the cavity of the mouth.

26. Bone in section where the two branches of the lower jaw have been sawn through.

27. One of the incisor teeth

28. The lower lip.

29. The dental pad—a thick cartilaginous pad which in ruminants represents the upper incisors of other animals.

■iO. The middle cartilaginous septum of the nose. This is covered by a membrane variously known as the pituitary, the olfactory, and the Schneiderian membrane. This membrane also covers the inside of the nasal cavities and the turbinated bones, the great ethmoidal cell or olfactory antrum, and is continuous with the mucous membrane of the pharynx.

Pituitary.— That which secretes mucus or phlegm. Latin, pituita , phlegm. Olfactory. — Latin, olfactum, to smell. Schneiderian.—Named after the anatomist who first described this membrane. Turbinated.—Latin, turbinatus , pointed like a cone. Ethmoidal. —Greek, ethmos, a sieve. The ethmoid bone is perforated like a sieve t( allow of the passage of the olfactory nerves. Antrum. —Latin, antrum, a cavern. Pharynx. —Greek, pharungx , a muscular pouch at the mouth which terminates in tht gullet.

This is a highly specialised membrane, in which the fibres of the olfactory nerve ramify. I'hc olfactory nerve is one of special sense —that of smell.

31. The maxillary turbinated bone. The turbinated bones are composed of compact tissue, but they are extremely thin and paper-like, and are so rolled upon themselves as to afford an extended surface for the display of the pituitary membrane.

32. The nasal bone.

33. The great ethmoidal cell, or olfactory antrum. This is very largely developed in ruminants, so much so as to appear almost like a third turbinated bone.

34. The ethmoidal turbinated bone

35. The ethmoidal volutes

36. The sinus or air-space between the outer and inner plates of the frontal bone. This communicates with the nasal cavity by means of two large circular openings which' traverse a very thin convoluted bony partition and open into the nasal chamber beneath the great ethmoidal cell. In the diagram, at Nos. 37 and 38, these two openings are traversed by probes, which serve to show the direction of the air-passages.

Maxillary. —Latin , 7 maxiila, the jaw. Nasal. —Latin, nasus , the nose. Volutes. —Latin, volutus , twisted : from volvo , I roll.

FIG. 111.

LONGITUDINAL SECTION OF THE THORAX.

Drawn by H. C. Wilkii

Entered at Stationers’ Hall, 1904

REFERENCES TO FIG. 111.

1. The tubercle of the first rib.

2. The head of the same rib.

Each rib articulates with two vertebrae by its head, which is received into an intervertebral articular cavity, as seen at No. 44, and the tubercle corresponds with a facet on the transverse process of posterior vertebra, No. 43.

3. The tongas colli muscle. Described under Fig. 11.

4. The oesophagus. This tube conveys the Food from the pharynx to the stomach. It is here seen on its course through the chest and penetrating between the two portions ot the right pillar of the diaphragm on its way to the stomach.

5. The great vena azygos. This is a long vein which commences in the region of the loins, passes along underneath the backbone, receiving numerous branches on the way Nos. 40,41, 12 —and empties itself into the anterior vena cava, No. 10.

t>. Middle portion of the first rib.

7. The trachea, or windpipe.

8. The first bronchus —the right lung having been removed.

U. ii«v /'I Wo ‘ s/ !). The entrance of the thoracic dad into the anterior vena cava. The thoracic duct is a tube which originates in the region of the loins, with an irregular dilatation called the cistern of pecquet, and empties itself into the blood-stream, as seen at No. 9. The fluid it contains it receives from two sources. The drainage of all the tissues of the body supplies lymph, which is conveyed to the duct by the lymphatic vessels, and the chyle, or nourishment from the digested food, which is conveyed from the intestines by the lacteal vessels.

10. The anterior vena cam. This is one of the two largest veins ot the body, and is the general confluent of all the veins of the head, neck, and fore extremity. Its blood, together with that of the posterior vena cava, No. 30, is poured into the right auricle of the heart, No. 11, from whence it is squeezed into the right ventricle. From here it is forced

Tubercle -Latin, tuberculum, a little lump or protuberance ; from tuber, a hump. : from through; phrasso, I hedge in. Azxoos^— or unattached. Trachea.— Greek, tracheia , the windpipe. Bronchus.— Greek, brongchos , a windpipe. Si-Litin.Sffto contain milk. The lacteal vessels convey a milk-like fluid, the chyle. CAVA.-Latin cauus, hollow. muscular cavities of the heart are A "ssa^Sii£S£.'sruSia-s-»... ..» ~ Ventricle.— Latin, vcntriculux , the belly.

by a powerful contraction of the muscular walls of the ventricle through the lungs, where it passes into capillary vessels which penetrate into every part of the lungs and form close networks surrounding the air-cells at the terminations of the breathing-tubes.

The walls of both the capillaries and the air-cells are extremely thin, and through them the blood parts with carbonic-acid gas —the product of decomposition of tissue—and receives oxygen from the air with which the lungs are filled. Thus venous blood — i.e., blood from the veins—is changed into red arterial blood charged afresh with oxygen, which if conveys to the tissues by means of the arterial system.

The centre of. this system is the left side of the heart, into the auricle of which the revivified blood is poured. From here it is forced into the left ventricle, the muscular walls of which are extremely thick and strong. Contraction of the ventricle forces the blood into a very large vessel, the common aorta. The common aorta soon divides into two large branches, the anterior aorta and the posterior, and From these the arteries and arterioles convey the blood to all parts of the system.

11. The right auricle. The heart is a muscular organ which is divided into four compartments —an auricle and a ventricle on either side, right and left. The right side of the heart, as previously explained, receives the venous blood from the system, and passes it to the lungs ; the left also receives the blood from the lungs, and passes it to the system. lo prevent the backward flow from the aorta and pulmonary artery into the ventricles when these are relaxed, the opening of each of these vessels is guarded by three strong flaps — the semiluna valves. The openings between the auricles and ventricles are guarded in a similar manner that between the right auricle and ventricle consisting of three flaps (the tricuspid ), and that between the left auricle and ventricle of two flaps (the bicuspid or mitral).

Action of the Heart. —The pulse-rate of the sheep normally is from seventy to eighty beats per minute in the adult, and

Capillary.— Latin, capillus, a hair, a hair-like vessel. Aorta.— Greek, aorto, suspended: from aiero, I raise. Pulmonary.— Latin, pulmo, a lung. Semilunar. —Latin, semi, hall; luna , a moon. Tricuspid. —Latin, tris , three ; cuspi. s, a point. Bicuspid.— Latin, bis, two or twice; cuspis, a point. Mitral.— Latin, mitra, a mitre.

about ninety in the young. The action of the heart is characterized by two sounds and a pause. The two sounds are a long dull one, usually known as the first, and a short abrupt one, known as the second. The first sound is caused by the vibration of the column of blood in the ventricles and of the rendering tense of the auriculo-ventricular valves by the contraction of the ventricular walls. The second sound is caused by the sudden tension of the semilunar valves. Each phase of the heart’s action is accompanied by the following phenomena ;

I. With the first sound—

(1.) Contraction of the ventricles

(2.) The auriculo-ventricular valves are closed

(3.) The semilunar valves are opened, and blood is forced into the pulmonary artery and the aorta.

(4.) The auricles begin to dilate

(5.) The impulse is felt

.2. With the second sound

(1.) The semilunar valves are closed

(2.) The auriculo-ventricular valves are opened

(3.) The auricles are filling

(4.) Some blood is obtaining entrance to the ventricles.

3. With the pause—

(1.) At first blood is entering both auricles and ventricles.

(2.) The auricles now contract, filling the ventricles and opening the auriculo-ventri-cnlar valves widely.

(3.) The semilunar valves are closed

In accelerated beating of the heart the frequency depends mainly upon the length of the pause.

12. The left lung

13. The first bone of the sternum. The sternum, or breastbone, consists of six hones or sternibrte firmly united together by strong cartilage.

14. The pericardium, a membranous sac which encloses the heart. Its function is to fix that organ in the thorax and facilitate the cardiac movements bv offering a smooth moist surface.

Sternum.- Greek, sternon, the breast, Stf.rnibr/E. —The bones of the sternum. Cartilage —Latin, cartilage, gristle. Pericardium. —Greek, peri, round about; kanlia, the heart. Cardiac. -Of the heart. Greek, kardia, the heart.

15. The second of the sternibne.

16. Fat.

17. The sixth of the sternihne

18. Pat

19. A cut portion of rib.

20. Ditto,

21. Ditto,

22 The edge of the liver, as seen behind the ribs. o

23. The pericardium

24. The right ventricle of the heart

25. The liver

26. Fa

27. The diaphragm, a partition separating the thoracic from the abdominal cavity. This is a partly muscular and partly tendinous structure. It is the chief muscle of inspiration, as in contracting it recedes, draws the ribs outwards and forwards, and in this way increases the capacity of the chest.

28. A portion of the left auricle of the heart

29. The tendinous portion of the diaphragm which occupies the central part limited by the irregular outline in the diagram—all the rest consists of powerful muscular tissue.

30. The posterior vena cava

31 and 32. Two large branches of the pulmonary artery in the right lung. The remainder of this lung has been cut awav.

33. A portion of the second bronchus

34. The twelfth rib

35. The thirteenth rib.

36. The external intercostal muscles. These are muscles of inspiration, and, as is seen in the diagram, their fibres take a downward arid backward direction. The internal intercostals, which lie immediately below them, have a downward and forward direction. These are muscles which assist in forced expiration.

37. The posterior aorta.

38. The thoracic duct.

39. A large lymphatic vessel from the largest of the bronchial lym phatic glands, passing into the thoracic duct.

M), 41, and 42. Veins entering into the great vena azygos

43. A facet on the transverse process of a dorsal vertebra for the reception of the tubercle of the second rib.

14. The intervertebral facet, for articulation with the head of the second rib.

Intercostal.—Latin, inter , between ; costa , a rib. Lymphatic.—Latin, lympha , water, water-like.

FIG. IV.

DIAGRAM OF THE FŒTAE LAMB AS IT LIES IN THE UTERUS OF THE EWE IMMEDIATELY BEFORE BIRTH.

Entered at Stationers’ Hall, 1904.]

[Drawn by H. C. Wilkie.

REFERENCES TO FIG. IV.

The period of gestation or pregnancy is that during which the female carries its young in the uterus. Its average duration in the sheep is 119 days. A few instances have been known and recorded by Magne where the period has not extended beyond 143 days, while Baumeister and Reuff give the maximum period as 160 days. It has been found that generally the male lamb is carried about one day longer than the female, and twins a day less

A. The uterus

During gestation certain changes take place in the general thickness, form, situation, and direction of the uterus. The blood-vessels become greatly enlarged in size, the coats of the arteries being much thickened to admit of the increased distension ; the veins undergo even more enlargement than the arteries. The nerves of the uterus become considerably increased in size and anastomose freely. The whole uterus is much thickened and rendered denser. The uterus of the sheep presents upon its inner surface a number of very vascular tufts or cotyledons, which are slightly concave in the centre.

R, The chorion. This is the outer envelope of the foetus. It is a great membranous bag, completely closed, which corresponds to the inner face of the uterus. It has upon its surface a number of placeutuUe or cotyledons, which are intimately attached to the cotyledons on the uterus.

C. The allantois is a membranous bag, the middle portion of which passes into the body of the foetus. Here it forms the urinary bladder, and the tube communicating with the outer and larger portion is called the urachus.

Towards the end of pregnancy the sac of the allantois is filled with the foetal urine. Prior to this it contains allantoic fluid, which probably serves the purpose of nourishment.

Gestation. —Latin, gestalio, a bearing; gesto, 1 carry. Uterus. —Latin, uterus, the womb. Anastomose. —To unite one with another, Greek, ana, through ; stoma, a mouth. Chorion. —Greek, chorion, skin or leather-like. Allantois. —Greek, allantos, of a sausage. Pcetcs.— The young animal in the womb. Latin, feetus, pregnant.

D, The amnion is the inner membranous covering of the foetus. It is a closed sac, and contains liquor avnnii, an albuminous, alkaline fluid, in which the foetus floats, attached only at one point, the umbilicus. The purposes which the liquor amnii serve are important.

(1.) It forms a water bed for the developing animal and favours its movements.

(2.) It preserves an even temperature

(3.) It counteracts the effects on the foetus of movements by the dam.

(4.) It protects the dam, towards the end of pregnancy, from the movements of the foetus.

(5.) It is the principal agent in promoting the dilation of the month of the uterus at the time of parturition, and it protects the foetus from injury.

E. The foetus

F. The urachus

G. One of the umbilical arteries

H. The second umbilical artery

I. The umbilical vein. This vein has no valves. The umbilical cord, or navel-string, consists of an allantoic portion, the urachus, P, two arteries, G, H, and a large vein, I, imbedded in embryonic connective tissue (Wharton’s jelly) and a covering by a portion of the amnion. The placenta in the sheep, as in other ruminants, is a multiple one, and consists of about eighty placentulee or cotyledons. In them the capillary vessels containing blood from the foetus come into contact with capillary vessels containing blood from the dam, and an interchange of elements takes place by which the foetal blood is revivified and passes hack to the young animal to supply it with nutriment and the benefits of respiration.

Amnion. —Greek, amnion, a vessel for receiving the blood of animals in sacrifice Umbilicus. —Latin, umbilicus, the navel. Urachus. — Greek, miron, urine ; echo, I hold. Placenta.— Greek, plakous, a flat cake. Capillary.— Hairlike. Latin, capillus, a hair.

Bv Authority: John Mackat, Government Printer, Wellington.