310 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



The Test Proper. From 0.5 to 1 gram of the placental tissue to- 

 gether with 2 or 3 c.c. of the serum is placed in one of the diffusion 

 tubes (A) that has previously been adjusted in a small cylinder 

 containing about 15 to 20 c.c. of distilled water, and both the serum 

 and the outer fluid covered with a layer of toluol. A second tube 

 (B) is similarly arranged, but receives serum only, and no placental 

 tissue, while in a third tube (C) placental tissue is placed together 

 with 2 or 3 c.c. of the water in which it was kept, all the tubes and 

 cylinders being guarded against putrefactive changes by the addition 

 of a liberal quantity of toluol. The three cylinders are then placed 

 in the incubator and left for twelve to twenty-four hours, when the 

 dialyzate (10 c.c.) is tested for biuret as described. If the test is 

 satisfactorily positive tube B and C should give a negative reaction 

 and A a positive reaction. 



Results. Abderhalden claims that a positive reaction may be 

 obtained in every case of pregnancy even as early as the first month 

 and that the reaction persists until about the end of the first week 

 of the puerperal period. Corresponding results were reached in 

 pregnant cows, dogs, guinea-pigs, and rabbits (when a homologous 

 placental antigen must of course be used) . Other observers who have 

 repeated Abderhalden' s work have obtained corresponding results 

 and it would seem that the method may be regarded as one whose 

 value is already beyond dispute. 



That the same principle may be of use in the diagnosis of patho- 

 logical conditions also seems quite possible and Abderhalden himself 

 has already pointed out that cancer would suggest itself as a profitable 

 field for investigation along these lines. 



ALLERGIC REACTIONS 



By the term allergic reaction in the clinical sense we understand 

 the specific symptomatic response on the part of the infected and 

 hence sensitized organism to the parenteral reintroduction of the cor- 

 responding antigen. Among the infectious diseases such reactions 

 have been notably studied in connection with tuberculosis, but are 

 evidently destined to play an important role in the diagnosis of 

 other diseases as well. In the present work we shall confine our 

 attention to the tubercular test and the luetin reaction in their 

 relation to the diagnosis of tuberculosis and syphilis respectively. 



