PRACTICAL DAIRY BACTERIOLOGY.

Manawatu Herald, Volume XXX, Issue 3786, 8 February 1908, Page 3

PRACTICAL DAIRY BACTERIOLOGY.

Only within comparatively recent times has it become generally known to dairy farmers that many of the changes, which take place in the character of milk when kept for a short time exposed to the air, are due to the presence and operation in it of invisible animated organisms known by the general term bacteria. These minute form of life have attracted the attention of students and scientists with the result that recognition has been given to the science of bacteriology. It has not quite attained its majority, for only in 1890 was it determined that the subject had a large field of practical application. Its importance in con : nection with dairying has increased the attention paid to it. A recently published volume is of a singularly interesting and instructive character. In the first part of it the author discusses the matter arising in the dairy proper and concerning the relation of the bacteria in milk; and in the second part he deals with problems arising out of the relation of bacteria to milk supplied to communities. Bacteria, it is generally understood, are organisms, living things, invisible to man’s eye without the use of a magnifying glass or microscope. Professor Conn says .while a microscope is desirable it is not absolutely necessary, because the objects must be handled in masses. For a student a microscope is necessary, as a space the size of a pin’s head may accommodate eight thousand millions. They are colourless, and have to be stained to become visible. Cultivated colonies form the basis of bacteriological study. Having introduced the bacteria in this way, the author proceeds to describe their shape, powers of motion—some are stationary, others are capable of a sort of swimming motion —their mode of multiplication by division, and production of spores. The distinction between yeasts and moulds and bacteria is explained. After long discussion it has not yet been definitely concluded whether bacteria are plants or animals, but the opinion is that they are plants of a low type. The conditions favourable to bacterial life are explained, and then attention is given to the types found in milk. It is impossible to obtain milk from a cow, no matter how cleanly the conditions, without bacteria appearing in the pail. There are certain normal bacteria always to be found in milk ; and abnormal varieties that are only present in special circumstances. The souring of milk in a thunderstorm is due to the high temperature enabling the bacteria to be particularly active. Lactic acid bacteria are the kind that make milk sour,- but how many species there are it is impossible to say. The most prominent variety is Bacterium Lactis Acidi. Modes of isolating ard dealing with it are described, and other varieties are noticed in such a way that the reader cannot fail to be interested. The means by which bacteria can be increased by dirt on the cow, in the air, in milk vessels, are commented upon. An instructive chapter is devoted to the growth of bacteria in milk ; and another to the presence in milk of the germs of tuberculosis, typhoid fever, diarrheal diseases and toxic poisoning from milk products. Having in this manner dealt with bacteria scientifically, Professor Conn proceeds to elaborate the second portion of his work, and in five chapters discusses dairy methods ; treatment of milk for market: public problems, such as the purity of the milk supply for cities, the use of a standard, dairy inspection, and compulsory pasteurisation ; bacteria and butter-making ; and bacteria in cheese. A concluding chapter of 148 pages gives laboratory directions for experiments in dairy bacteriology. From what we have said it can be understood that this is a work of more than ordinary interest to practical dairymen on the one hand and to the health authorities on the other.' The science in it is of such a character as to prove useful to all engaged in milk production. Students of dairying in State farms, dairy factories, and agricultural colleges will find the concluding chapter most instructive. By mastering its contents earnest workers will be able to carry out the bacteriological analysis of milk products that may be needed in a dairy, a factory, or a sanitary laboratory.