416 COLLECTED STUDIES IN IMMUNITY. 



It can be carried out exactly with only a very small number of readily 

 determinable substances, hence primarily with inorganic combinations. 

 Besides, the demonstration that a poison, for example arsenic, occurs 

 in a certain organ, as the brain, is of little value, for this does not 

 tell us what is really of the greatest importance, namely, the localiza- 

 tion in the separate cell constituents of the various organs. 



The pathological and histological findings are of far greater 

 importance. To be sure, if one turns the pages of the text-books, 

 one will not have very great hopes in this direction, for the same 

 banal changes, fatty degeneration of the liver, nephritis, destruction 

 of the blood, are always given. NissFs investigations, however, 

 demonstrated that exact histological studies on the central nervous 

 system allow the points of attack to be recognized. He showed that 

 certain poisonings always affected certain groups of ganglion cells. 

 How fruitful these points of view may be was shown by the pretty 

 investigations of Goldscheider, through which he showed that the 

 motor ganglion cells had already suffered demonstrable lesions from 

 tetanus poison at a time when even the slightest clinical symptoms 

 were absent. In many other cases also, most valuable information 

 may be furnished by minute histological investigations; in this 

 connection I may mention that with cocaine I have found in mice 

 an absolutely specific foam-like degeneration of the liver cells in a 

 form which I have seen with no other substance. In general, I may 

 add that the chronic poisonings extending over several days, and not 

 the acute poisonings, are best suited for the demonstration of specific 

 injuries to certain organs, a point which has already been emphasized 

 by Nissl. 



In my pharmacological investigations, which far antedate Nissl's 

 publications, I have given this method special preference. I also 

 described a method (Deutsche med. Wochensch. 1S90 ; No. 32) by 

 which these otherwise laborious experiments can be carried out with 

 ease. This method depends on feeding mice with biscuit which con- 

 tains a certain amount of the substance in question. It is then very 

 easy to find a dose which will kill the animals in the desired period 

 of time. 



Although the results of these anatomical-pathological investiga- 

 tions are most valuable, it cannot be gainsaid that through them 

 one only discovers the injury to the most susceptible organs, but 

 that the general distribution of a certain substance within the entire 

 organism remains unknown. 



