Zymotic and Germ Diseases. 255 



zation of the different tribes of these bacteria, which renders it possible 

 to cultivate and study them separately. This has been, and is being 

 done, to the incalculable advantage of the human race, by many such 

 men as Pasteur and Koch Nature's Nobility. Like causes always pro- 

 duce like effects, and the cultivation of microbes or the propagation of 

 a disease wit/umf <-li<inge in their 'character, depends upon the mainte- 

 nance of it/cut leu/ cnmlitlons. Professor Tyndall in speaking of the work 

 of Pasteur in the cultivation of unmixed races of these "germs " says : 

 "By teaching us how to cultivate each ferment in its purity, in other 

 words, by teaching us how to rear the individual organism apart from 

 all others, Pasteur has enabled us to avoid all these errors. And 

 where this isolation of a particular organism has been duly effected, it 

 grows and multiplies indefinitely, but no change of it into another or- 

 ganism is ever observed. In Pasteur's researches the Bacterium re- 

 mained a Bacterium, the Vibrio a Vibrio, the Penicillium a Penicillium 

 and the Torula a Torula. Sow any of these in a state of purity in an 

 appropriate liquid ; you get it, and it alone in the subsequent crop. In 

 like manner sow small-pox in the human bod3 r , }*our crop is small-pox. 

 Sow there scarletina, and } T our crop is scarletina. Sow t}'phoid virus, 

 your crop is typhoid; cholera, your crop is cholera." This statement is 

 true ; the first part of it literally so. But we must not get from it an 

 impression that there is absolute and invariable constancy in the repro- 

 duction of these organisms, because it certainly cannot be main- 

 tained that they are any more constant or breed "truer" than other and 

 higher organisms, visible and tangible. 



Prof. Tyndall provides that they be sown in an appropriate liquid ; 

 and this is the saving clause, for if it be not appropriate we can 

 depend upon it the organism will be more or less perverted. It is cer- 

 tainly a fact that these small organisms are far more at the mercy of their 

 environment and subject to far greater changes from it in proportion to 

 their size, than are larger and more complex organisms. Organic chem- 

 istry informs us, that the alteration of an atom in a body consisting of a 

 single molecule, may make a totally different thing of it. The action 

 of its environment upon every organism, big or little, produces in it 

 atomic alterations. Everj r movement of an organism involves atomic or 

 molecular displacement and changes the organism by that much, and it will 

 remain changed unless its virility and individualism enables it to recover. 



Papillon remarks that the yeast cells which produce alcohol in differ- 

 ent fruits are slightly different in form from one another, and from those 

 of grape, must or beer-wort, these variations being due to the medium 

 acted upon as the different fungi, will grow in any one of the media. 



If putrid matter containing vibrios be injected under the skin of a 

 dog, they will grow in the blood, reproducing with great rapidity until 



