Bactériologie laitière pratique, prête à l'usage des étudiants, producteurs, et tous les intéressés par les problèmes de la relation du lait pour la santé publique . annonce peut détenir 8 000 000 000 et 100 000,-000 aura beaucoup de place dans une goutte de lait. Cette extrememinuteness doit toujours être gardé à l'esprit dans les tentatives de sous-stand. Cette minutie, il est impossible de les gérer. vidually-indi La seule façon de traiter avec eux est d'handlemasses, et des méthodes de laboratoire commencent toujours par cultivatingthem, c'est-à-dire, les mettre en conditions wherethey va croître jusqu'à ce qu'un grand nombre peut être ob

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Practical dairy bacteriology, prepared for the use of students, dairymen, and all interested in the problems of the relation of milk to public health . ad may hold 8, 000, 000, 000, and 100, 000, -000 will have plenty of room in a drop of milk. This extrememinuteness must always be kept in mind in attempts to under-stand them. This minuteness makes it impossible to handle them indi-vidually. The only way we can deal with them is to handlemasses, and laboratory methods always begin with cultivatingthem, by which is meant, putting them into conditions wherethey will grow until large numbers may be obtained. Suchmasses or cultures we can easily deal with, and for this reason, in spite of the fact that they are the smallest known living WHAT ARE BACTERIA? thing, most of the methods of bacteriological study do not eveninvolve the use of a microscope. The unit with which the student commonly starts is not abacterium, but a colony. By reference to experiment No. 6 itwill be seen that a colony is a mass of bacteria in some solidjelly medium. (Fig. 2.) Such a colony is composed of thou-sands of bacteria, all of which are supposed to have risen from. FIG. 2—VARIOUS TYPES OF COLONIES OF BACTERIA GROWING ONGELATIN a single bacterium by multiplication. The whole makes acluster big enough to be seen without any lens, and since allthe bacteria in it have come from a single one they are allalike. The colony may be picked out of the jelly, placed in somemedium in which the bacteria will thrive, and then, afterproper growth, the bacteria can be studied by the microscope.Such cultures form the basis of bacteriological study. Form of Bacteria.—Bacteria are of three quite differentshapes, but all very simple, i. Simple spheres. (See Fig. 3, b, c, d.) Such spherical forms are called cocci, and in PRACTICAL DAIRY BACTERIOLOGY common microscopical preparation no internal structure can beseen, the bacteria appearing as faint stained balls. The cocci, however, differ somewhat in their method of

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