LECTURE XXX. 



OUTLOOK. 



II. 



WE have seen in discussing the boundaries of physiological-chemical 

 investigation, that such exist only artificially, and that the domain is 

 immensurable. The tendency is becoming more and more marked to refer 

 sciences which were formerly sharply defined to a common basis. This is 

 particularly true in the domain of pathology, which is becoming more and 

 more closely related to physiology. In fact, pathological processes in a 

 certain sense are nothing else than physiological processes of our body- 

 cells under specific conditions. This applies particularly to a group of 

 processes, interesting alike to pathologists and physiologists, namely, the 

 formation of certain substances in response to the action of other products 

 on the body -cells. We have already encountered these processes at various 

 times. We have seen that the animal organism responds to the intro- 

 duction of ferments by the formation of anti-ferments; that is, the cells 

 produce substances which prevent the activity of the ferments. We again 

 met this problem in considering the so-called " biological reaction. " 

 Here also, it was a case of the formation of distinct metabolic products. 

 The most significant thing about these processes is the fact that the 

 products formed act in a very specific manner. We thus involuntarily 

 return to an analogous process which we have already mentioned. It is 

 known that the human and animal organism is capable, not only of 

 withstanding the infection of specific pathogenic bacteria, but also, that 

 it possesses peculiar characteristics, which prevent a second attack of the 

 same bacteria for a long time after their first repulse. This, of course, 

 only applies to certain infectious diseases. Other diseases do not leave 

 such a condition of affairs behind them. This is evident from the fact 

 that one may be afflicted several times with the same disease, e.g., 

 pneumonia, whereas other sicknesses, such as typhoid or scarlet fever, 

 usually occur but once. 



The far-reaching specificity is also noticeable in these cases. This is 

 best demonstrated by the following example. We can determine, by 

 experiment, the quantity of cholera bacteria necessary to cause the death 

 of a guinea pig of a given age and weight. If we take a smaller quantity, 

 the animal will only become sick, and will gradually recover. This guinea 



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