ANTITRYPSIN TEST 265 



several drops of acetic acid solution to each tube, and again observe the 

 tube containing the smallest amount of trypsin in which cloudiness can 

 be seen. In this way the amount of trypsin neutralized by the anti- 

 trypsin of the serum is determined. 



For example, in an experiment the preliminary titration showed that 

 0.5 c.c. of trypsin completely digested the casein. In the second part 

 of the test the lower limit of trypsin was this 0.5 c.c. increased by 0.1 

 c.c. in successive tubes up to 1 c.c. It is now found that 1 c.c. of the 

 trypsin solution is required to bring about the complete digestion of the 

 casein in the presence of the serum, or 1 c.c. 0.5 c.c. =0.5 c.c., which is 

 the amount of trypsin neutralized by 0.01 c.c. of undiluted serum. 



A control experiment is conducted with the pooled serum of several 

 normal persons, and a comparison of the value thus obtained shows 

 whether the antitryptic power of the serum tested is altered. 



The method of Marcus, 1 which is a modification of the method of 

 Muller and Jochmann, 2 is described in the laboratory exercises on 

 Experimental Infection and Immunity. 



ABDERHALDEN'S SERODIAGNOSIS OF PREGNANCY' 

 Methods. Two methods have been devised by Abderhalden for 

 the demonstration of the ferments in the blood-serum of preg- 

 nancy : 



1. The Dialyzation Method. Specially prepared and coagulated 

 placenta and fresh serum are placed in a dialyzing capsule so prepared 

 that it will permit the passage of peptones and amino-acids only. The 

 filled capsule is placed in sterile distilled water, and incubated for from 

 sixteen to twenty-four hours, when the dialysate is tested by the biuret 

 or ninhydrin test for peptones and amino-acids. Under proper condi- 

 tions the presence of these substances indicates that the placental tis- 

 sue has been digested by the serum. 



2. The Optical Method. This method is based upon the same prin- 

 ciple as the dialyzation method. Into the tube of a polariscope place a 

 solution of placental peptone and the serum to be tested. Warm the 

 mixture to 37 C., and after an hour note the degree of rotation and 

 record it; repeat this at intervals during the following twenty-four to 



1 Berl. klin. Wochenschr., 1908,- No. 4; 1909. 



2 Munch, med. Wochenschr., 1909, Nos. 29 and 31. 



3 Abderhalden: Abwehrfermente des tierischen Organisims, Julius Springer, 

 third edition, 1913. 



