16 D. H. ATTFIELD THE LOWER MICRO-ORGANISMS. 



tliroiigh successive generations of the organism, (c.) A pure culture 

 thus obtained must, when introduced into the body of a healthy- 

 animal, produce the disease in question, (d.) Lastly, in the inocu- 

 lated animal the same micro-organism must again be found. 



[In the course of the lecture a large number of photographs of 

 the better-known bacteria were shown by the aid of the oxy- 

 hydrogen lantern. The following are a few of the species 

 exemplified, with the remarks made upon them.] 



Proteus vulgaris, Bacterium termo, and Spirilhim undida. — These 

 are intimately associated with the phenomena of putrefaction. 

 They are of the highest importance to man, and may well come 

 under the title of invisible friends ; for they utilise the excretions 

 of living beings and the carcases of dead animals and plants, after 

 breaking them down into their simplest constituents, to supply 

 those elements which are necessary for the nutrition of plants ; 

 thus, from dead organic matter producing the food which is 

 necessary for the vegetables, which are in their turn the food 

 of animals. 



SarcirKe, Bacterium fgurans, Spirillum tenue, and S. volutans. — 

 These are, if not active friends, certainly not dangerous enemies. 



Bacillus antJiracis.— This is the direct cause of wool-sorters' 

 disease in man, and what is known as splenic fever in cattle. 



Koch's '■'■comma lacillusy — Whether this is the true cause, or 

 only an attendant circumstance, of Asiatic cholera, is still the 

 subject of active discussion. Professor Max von Pettenkofer used 

 to say of this bacillus, of which both he and his colleague, 

 Professor Emmerich, of Munich, ate a considerable quantity 

 without developing cholera, or indeed suffering from any un- 

 pleasant consequences: "To produce an attack of cholera three 

 things are necessary — (1) the bacillus, (2) a suitable soil for it to 

 grow on, that is, a person in a susceptible condition, and (3) a 

 tertixim quid.'''' What this "third something" was, my old master 

 Yon Pettenkofer did not pretend to say, but he was convinced that 

 without it one did not catch cholera. 



The '■'■tubercle hacillus.'''' — This is perhaps one of the most 

 dreaded of our foes among the micro-organisms. It is the cause 

 of that fatal and widespread disease, consumption, or, as it is more 

 scientifically tenned, tubercular disease. 



