COMMUHICATIONS." 331 



The globular and oval forms are in a general way classified by 

 themselves, under the general name of Micrococcus ; the short rod- 

 like kinds are called Bacterium ; the straight, fiber-like are called 

 Bacilli IS ; the curved and wavy, Vibrio; and the spiral, Spirillium. 

 For a long time many regarded these varied forms as but differ-, 

 ent stages of growth of one and the same organism, and that the^ 

 little differences seen in what might be called the same stage were 

 due to more or less favorable conditions for development, but the 

 most careful investigation has demonstrated that each is but the 

 characteristic form of a separate species ; that while there is a gen- 

 eral resemblance in the spore state of all kinds, and that the spores 

 of all are similar to the mature form of the class called Micrococ- 

 cus^ each variety has its peculiar characteristics and workings, as 

 permanent and distinct as is seen in the higher orders of plant 

 life. This conclusion has been reached through experiments in 

 the separate cultivation of the different varieties, planting the 

 individual germ in a fluid containing the necessary nourishment, 

 giving the proper temperature and watching it through all its stages 

 of growth. Owing to the difficulty of destroying all germs in the 

 nourishing fluid, and of excluding those in the air, great care is 

 required, and uniform results have not always been reached in 

 these experiments. Some claim that the deadly Bacillus Anthrax 

 found in splenic fever can be changed by different treatment and 

 a change of nourishment into the IJacilhis suhlilis, an innocuous 

 germ, common in all infusions of hay, and also the reverse, but 

 the general belief is that no change of nourishment, or other con- 

 ditions will produce a change in the form of mature development; 

 that like must come from, and must produce like. 



There is perhaps as great a difference in their size, if such a 

 thing can be conceived of in bodies the largest of which is 

 microscopic, as in their form. Take the Bact&rium ierrmo, the 

 germ found in most all forms of putrefaction, and which is said 

 to be the active agent in all kinds of fruit tree blight, it is far 

 from being the smallest. An adult germ of this variety has an 

 average length of 18,000th of an inch and a diameter of 16,000th. 

 To make this appreciable by figures, try to cover a surface of an 

 inch square with them, placing them compactly, end to end and 



21 — HORT. 



