2 INTRODUCTION. 



it at once became evident how the physiological phenomena of nutrition 

 and production of energy are identical in their nature with processes which 

 under pathological circumstances lead to the formation of anti-infectious 

 bodies. In an analogous and no less ingenious manner, Metschnikoff has 

 shown that the same cell group of mesenchymal origin which the organism 

 stations against bacterial invasion has physiological and physio-patho- 

 logical functions to fulfill in the whole animal scale. In the lower animals, 

 these cells aid in the metamorphosis of the body structure, thus leading to 

 the disappearance of entire organs. In the female, they aid in the involu- 

 tion of the uterus after labor, while in the aged, they destroy the nerve cells 

 in the senile atrophied nerve centers or finally as chromophages turn the 

 hair gray. The border-line between the physiological and pathological status is 

 biologically not sharply demarcated. It is one single chain of manifestations 

 which possess numerous transitional phases. As the methods of serum 

 diagnosis can prove reactions much finer even than those accomplished by 

 chemistry, their application has not been limited to the chapter on infectious 

 diseases. 



By their means also, proteids, even though manifest in minutest traces, 

 can be differentiated. Similarly, the secret of blood relationship has begun 

 to be unravelled; and there is a possibility even of solving the problems of 

 metabolism. 



Closely associated with serum diagnosis is the serum therapy. Even 

 though the general application of the latter is not as widely developed as 

 that of the former, it must be remembered that through this medium diph- 

 theria has been transformed from a fatal to a combatible disease, and 

 incidentally made the name of Behring immortal. To-day, attempts are 

 constantly being made to treat other bacterial and toxic diseases by specific 

 therapy and it is to be hoped that success will soon be met with. 



The study of serum therapy and serum diagnosis is undertaken in 

 various ways. It is comparatively simple to learn only the purely technical 

 details. All large laboratories have trained assistants for the performance 

 of certain reactions or groups of reactions with absolute precision. Although 

 as we have said, they do such work as assigned to them, with accuracy, they 

 are nevertheless far from a thorough understanding of the subject of serum 

 diagnosis. Unfortunately this blind method of procedure has recently 

 been advocated to an alarming extent. In addition, the practical success 

 which the Wassermann reaction has met with, has inculcated the desire in 

 certain schools of physicians, for the carrying out of this test alone, and thus 

 to become independent of the use of large laboratories. To meet this 

 demand, short courses have been established and the serum diagnosis of 

 syphilis taught with lightning rapidity. That such a state of events is 

 absolutely injurious is clearly evident. It is impossible for one to be a 

 specialist in a certain reaction and at the same time be ignorant of the other 



