236 Physical Chemisfry and the Doctrine nf Immunity. [June 9, 



of animal from which a given blood-spot is derived, instead of the 

 older method of Wassermunn and Uhlenlmth, in which the pre- 

 cipitate itself was ol)served. The new method, which was worked 

 out by Neisser and Sachs, plays a highly important role in the method 

 of Wasserman for determining the presence of spirochgetes or, Ijetter, 

 their excretions in human blood. 



As will be seen from what has lieen said, inmiuno-chemistry 

 has, during its short time of application, been able to explain the 

 chief empirical facts of immunity, and there is good reason to hope 

 that it will be al)Ie to throw light on the whole of that important 

 branch of therapy and to transform it into a rational science. 



Physical chemistry itself has thereliy gained a great extension 

 of its sphere, not only as regards chemical equilibria, but also as 

 regards the studv of velocities of action. 



