88 THE DISEASES OF DOMESTIC ANIMALS. 



placed upon a glass slide and covered, the active bacteria will all 

 gradually approach the margin of the cover, and at the end of sev- 

 eral days will be found ah've, while those situated toward the center 

 will be dead." 



Toussaint, the ablest veterinary student of this subject, has re- 

 cently published the following results with reference to B. anthracis : 



" The bacteria which occupy the central portion of Kanvier's 

 moist chamber, and which by reason of their situation receive very 

 little oxygen from the groove, are soon arrested in their develop- 

 ment, while those which occupy the borders are long and collect in 

 immense numbers. Those in the center remain small, formed of 

 two, four, or five articulations, which are easily separated. They 

 soon cease to grow, and are not transformed into spores." 



Cohn, an unquestionable authority, also says that "the com- 

 plete development of bacillus, and, above all, the generation of 

 spores, only take place under the free access of air." 



Reproduction of Bacteria. 



"We have already mentioned that bacteria reproduce either by 

 scissiparity — fission — or by the endogenous production of spores, 

 which are again capable of developing into bacteria. We have 

 also frequently mentioned that these spores are so wanting in 

 specific characteristics that it is impossible to assert whether each 

 variety of bacteria has its own specific spore or germinal form, 

 although this theory is mostly supported ; while able authors also 

 hold to a metagenetic theory — that is, that a metamorphosis be- 

 tween the different forms of fungi is possible, the same being due 

 to the influence of the different media in which they may be culti- 

 vated or live. 



When proliferation takes place by fission, or transverse division 

 of the cell, we see the cell gradually yet rapidly increases in length, 

 the protoplasma in the middle becoming clearer, and a partition 

 forms in the middle of the cell, separating the protoplasma into two 

 distinct portions. The partition is at first very delicate, but soon 

 thickens, and the cell divides in two. 



This phenomenon takes place more or less rapidly, dependent 

 upon the richness in nutritive material of the media in which it is, 

 on the temperature, moisture, etc. 



In some cases a constriction takes place in the middle of the 

 cell, the two ends having a figure-8 or bulb-like form. 



