32 EXPERIMENTAL RESEARCHES 



in the direction indicated. The recent work of 

 Wassermann, who by means of complement- 

 fixation, was able to prove the existence in 

 the blood serum of anti-bodies for certain 

 nutritive substances (glycogen, albumoses, 

 peptones, etc.), and to obtain an increased con- 

 centration of these by increased doses of the 

 nutritive substances, appears to me to be very 

 promising. In the case of pathogenetic or patho- 

 gnomonic questions it does not appear to be 

 of use to seek for those haptines which may be 

 present in the blood as the result of immunisa- 

 tion ; for in their case one would either find 

 differences that are but slightly marked, or, if 

 one found sufficiently-marked differences, one 

 would have to be very careful in drawing con- 

 clusions from them. It would be better, there- 

 fore, to avoid using as test objects those sub- 

 stances which are already present in the normal 

 body, or gain entrance to it by infection. In 

 order to be able to draw absolutely correct con- 

 clusions as to the relations existing between 

 certain substances in the serum and the normal 

 or pathological activity of organs, one ought to 

 choose cells or other elements, regarding which 

 one may assume that they never come into 

 relation with the human body in a natural way. 



