ORIGIN OF DISEASE AND THE GERM THEORY. 



139 



contact with an abraded surface. In the course of ages parti- 

 cular kinds of schizomycetes, among which bacteria are included 

 — these are the names by which these germs are known — would 

 gradually tend to become more dangerous than others in the case 

 of some of the various groups of animals respectively. It is 

 quite probable that one kind of germ would become particularly 

 harmful for one kind of animal and another more especially dan- 

 gerous in the case of another group, and so on. It may possibly 

 be the case that germs which were once merely putrefactive 

 organisms gradually found entrance into the bodies of animals, 



Fig. 16 — From a Preparation of the Blood of the Spleex of a 

 Guinea-Pig dead of Anthrax. 1. White blood-corpuscle. 2. Red blood- 

 discs shrunken. 3. Chains of bacillus anthracis. 4 Degenerating bacilli, the 

 sheath only being preserved. Magnifying power 700. (The preparation had 

 been stained with gentian- violet. )^ — Klein. 



thus becoming pathogenic and often giving rise to fatal 

 diseases. In some such way as this we may suppose that 

 certain diseases originally arose. The life-history of septic 

 micro-organisms outside the animal body is not well known as 

 yet. The facts that they are modifiable by alterations of tem- 

 perature and by differences in the medium to which they are 

 subjected, supply us with clues which are being extensively 

 worked out. There are, for instance, some bacteria which, 

 under the influence of certain conditions of this kind, produce 

 definite pigments. From the results of his many experiments. 

 Dr. Klein concludes that there are some definite micro-organisms 

 which, as a rule, exist and grow in various substances, and also 



