324 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



no digestive properties for silk peptone, while the serum of an animal 

 that has been previously injected with such material is capable of 

 effecting its cleavage. Similarly we find that normal serum is incap- 

 able of bringing about the cleavage of cane sugar, while the serum 

 of an animal that has previously been injected with the carbo- 

 hydrate in question does this quite readily. Most extensive investi- 

 gations along these lines convinced Abderhalden that such a reaction 

 on the part of the treated animal is of invariable occurrence, and in a 

 general way this corresponds to our views regarding antibody forma- 

 tion, as set forth in the first part of this volume. Without entering 

 into the question regarding the possible identity of some of the 

 antibodies in the sense of Ehrlich with the digestive reaction products 

 with which we have just become acquainted, the thought naturally 

 suggests itself that any component of the body may in the end be 

 viewed as alien to other parts of the body, if it is placed in surround- 

 ings which are in reality alien to that particular component. It is 

 thus quite conceivable that the presence in the circulation of some 

 of the body's own cells or cell products might give rise to similar 

 reactions providing that the substances in question are really foreign 

 to the the interior of the bloodvessels, i. e., to the blood-plasma or 

 the blood-cells. As this takes place not only under various patho- 

 logical conditions, but even in health or during pregnancy, where 

 chorion cells have been shown to enter the circulation, it was natural 

 to put the question to the experimental test. As a result Abder- 

 halden announced that he succeeded in demonstrating that the 

 blood-serum of pregnant animals has acquired the power of causing 

 the cleavage of placental peptone and placental proteins. 



While his experiments were originally conducted by bringing 

 together the serum of the pregnant animal and the placental pep- 

 tone in the tube of the polarimeter, when a gradual change in the 

 degree of rotation could be noted as the cleavage took place, he 

 subsequently discovered that the same reaction can be demon- 

 strated by placing the placental tissue together with the blood-serum 

 of the individual in a dialyzing tube and then testing the dialyzate 

 for biuret. To this end the following procedure is recommended. 



Abderhalden's Test. Preparation of the Antigen. A fresh placenta 

 is stripped of its membranes, cut into small pieces, and washed 

 free from blood by kneading the material in running water. This 

 should be continued until the wash water that may be pressed out 



