WM. S. GOTTHEIL. 
486 
discoveries, d n< ^ b) r this mear, s placed practical surgery in a 
position of sciential? accuracy undreamed of in former times. 
And the third is that ol Koch, whose systematic methods and 
far-reaching discoveries opened the paths of limitless improve¬ 
ment which practical medicine has but just begun to tread. 
Wherever we turn in nature, the activity of t the bacteria 
is apparent. All the fermentations, all the putrefactions, 
most of the processes by which insoluble and non-assimllable 
material is prepared for the use of the higher bodies, many 
pathological processes—all are due to microbic life. The mi¬ 
crobes live upon matter, and secrete or excrete, as you will 
see from the various chemical substances that form the es¬ 
sence of these changes. The chemical action of the micro-or¬ 
ganisms is the key that will unlock for us many of the most 
secret processes of nature. 
The putrefactions were first thoroughly studied. A mul¬ 
titude of bodies, mostly poisonous, indol, skatol, cresol, car¬ 
bolic acid, were discovered to be formed by the successive 
broods of microbes that lived upon the putrefying material, 
and upon each other. They were called ptomaines or tox- 
ines. Soon these same products, these same organisms, were 
found in the human alimentary canal, and the whole intestine 
was found to be simply an immense centre of putrefactive 
change. ' 
Nevertheless, under normal conditions, these organisms 
and the poisons they produce do no harm. The chemical 
substances unite with the sulphur compounds, and become 
harmless. If, however, as in hyaemia, scarlatina, diphtheria, 
intestinal diseases, etc., the normal activity of the tissues is 
impaired, the putrefactive products are not neutralized, and 
they appear unchanged in the excreta. 
From the putrefying flesh of men, horses and cattle a long 
list of poisonous ptomaines has been obtained. Neuridin, 
cadaverin, putrescin, midatoxin, typhotoxin, neurin and me- 
thyl-guanidin are some of them. They are all bacterial pro¬ 
ducts. Thus the harmless creation, formed as a proximate 
principle in the flesh of all mammals, becomes, through the 
oxidizing power of the bacteria, methyl-guanidin, a violent 
poison that kills with convulsions of all the muscles. 
