VACCINATION EXPLAINED.

Auckland Star, Volume XLIV, Issue 178, 28 July 1913, Page 6

VACCINATION EXPLAINED.

FOB. THE KAN IN THE STREET. NATURE'S FIGHTING RESERVE". TO TACKLE A DREAD DISEASE. At the present time public attention is being directed with unwonted interest to what has been generally regarded as the mystery of vaccination, and why its practice should induce immunity from a dreaded and loathsome disease. -But in a general way there is no reason why an intelligent understanding of this much advocated safeguard should not be universal. Pathological research has thrown a great deal of light on the manner in which living bodies resist and recover from the attacks of disease; and increasing -knowledge of bacteria, as the cause of most infective disease, has been accompanied by increasing knowledge of effective modes of resistance to disease. It is a fundamental truth that, iv the case of certain diseases, one attack protects against subsequent infection. The body, once attacked, and able to resist the attack, sets up a <i "fence reserve, as it were. an*d is ready next time to show fight to the invading bacteria. This law of nature is aided by vaccination. A person who has heci' deliberately infected with vaccinia, or enwpox, a mild or attenuated form of smallpox, is thereby enabled to set up in his own body the defensive toxins which will be ready to destroy the virulent bacteria of smallpox should they attempt to claim him a suitable field for their ravages.

The actual germ of smallpox has not been certainly isolated, but bacteriologists, do not doubt that the disease is due to some living agent similar in nature to the organisms of other infective diseases,. The question of the identity or difference of smallpox and cowpox was long disputed, but there can now be little doubt that Jenner was right in holding that the latter is only smallpox modified by transmission 10 a different animal which is less suspectible to the disease. Many attempts have been made to transmit smallpox directly to cattle, and a certain number of successful results have been recorded. Adult cows take the disease with difficulty; calves aro more easily infected.

Vaccination consists in inoculation of an attenuated form of smallpox germs. the diminution in virulence being brought about by passage throngli the body of a calf, a less susceptible animal than man. The attenuated germs are prfnent in the lymph of the vesicles (or little blisters) formed on the vaccinated person, and this lymph may be used for inoculation of other individuals, as the germs do not regain their virulence by repaasag? through man.

Vaccinia (or e.owpoxi remains a localised disease, the attenuated germs remaining in the place of inoculation, and not becoming generalised by the bloodstream. At the point of inoculation they form their toxins, or, as it were, poisons, which are conveyed all over the body, and stimulate the tissnes to form germicidal substances. The cells thus educated retain the property of secreting these substances for a considerable length of time. Although, theoretically considered, it is immaterial from what source, human or bovine, the lymph is derived: the lymph got from an "animal" source is preferred in practice, and what'is known as ''glycerimtted calf-lymph" is chiefly used.

The preparation of thia lymph has a particular interest at the present time. A supply of stock lymph being alreadyavailable, a calf is taken and its abdomen is shaved. A series of incisions of considerable length are made in it. and the stock lymph is rubbed into them. By the fifth day large vesicles have developed along the ennrse of the incisions. and are full of dear fluid which docs not yet exhibit a-ny tendency to become pustular.

At this stage the vesicles and their contents are scraped off with a sterile sirarp spoon, -with all aseptic precautions, and the resulting material is collected in suitable bottles. It is next finely broken up. and triturated, or pulped, with four times its weight of glycerine and water. The thick, creamy fluid produced is run into tubes; and these are kept in a cold dark place for some weeks.

The result of 'this treatment is to kill off most of the pyogenic (pus-prodneinjr) and similar organisms which might do harm if inoculated: but few, if any, specimens of lymph are actually germfree The cont-agium of vaccinia is left apparently uninjured. After about a month the lymph is tested baeteriologioally to prove it free from the organisms alluded to; and. if it is found to be innocuous, it is drawn into capillary tubes, and is ready for use.

The lymph Hius prepared is a thick, syrupy fluid, which tends to separate to some extent into a clear and an opaoue portion. It is probable that the latter is the active part, and care should therefore be 'taken not to use only the clear portion in vaccinating.

The essential part of the process of vaccination is that the infected material —the lymph—should be introduced through the epidermis (the outer skin), so as to be absorbed by the lymphaTlcs and bloodvessels of the corinm (the inner or true skin). The site usually chosen is tbe skin of the outer side of the upper arm over the insertion of the tendon of the deltoid -muscle. The skin is wellwashed and dried. A tube of lymph is opened, and the whole of its contents ejected on to the clean skin. A sterile Inncet, or scarifyiiisr needle, is used to scratch the epidermis through the lymph (care being exercised to avoid drawing blood), and the lymph is rubbed into the scratches. More than one insertion is usually made to obviate risk of failure. The several sites are kept apart, so that the resulting vesicles may not coalesce and create an unduly sore arm. The "beautiful arm" so commonly seen after vaccination in the past century, was no criterion of efficient vaccination. ] t merely indicated the use of contaminated lymph, and the employment of septic methods of conducting the operation.

The bulk of expert opinion appears to favour the conclusion 'that vaccination confers ;:n active immunity against smallpox, and protects almost absolutely for a certain period of time. This immunity gradually diminishes, and in many cases disappears after a longer or shorter interval, which varies in different individuals. If duly sterilised calf-lymph be used, the danger of any ill-effects resulting is very small indeed. Complications are generally due to want of cleanliness and lack of care in tbe after-treat-ment of the lesions resulting from the inoculation. "Arm-to-arm" vaccination is nowadays utterly condemned