FERMENT REACTIONS 323 



through a Berkefeld filter, or, if the quantity be small, through a 

 Silberschmidt microfilter. 



THE EXAMINATION PROPER. Six tubes are placed in a suitable 

 rack and labelled I, II, III, IV, V, and VI. Tubes I and II receive 

 1 c.c. of the solution under investigation, III and IV 1 c.c. of two 

 control solutions made up from dried animal blood, i. e., from blood 

 which does not correspond to the antiserum that is used, e. g., cat or 

 dog blood, if the antiserum is antihuman in character, and which 

 has likewise been diluted so as to correspond to a 1 to 1000 solution 

 (see preceding section), V 1 c.c. of sterile 0.85 per cent, saline, and 

 VI 1 c.c. of a 1 to 1000 solution of blood (made up of dried material) 

 corresponding to the antiserum in question, i. e., of human blood, 

 if the antiserum was antihuman in character. To each tube, with 

 the exception of tube II (which is treated with 0.1 c.c. of normal 

 rabbit serum), 0.1 c.c. of the corresponding antiserum is then added 

 in such a manner that the serum flows down the side of the tube 

 and does not drop directly into the fluid below. The tubes are now 

 allowed to stand at room temperature and without shaking for 

 twenty minutes, when the final reading is made. If the result is 

 positive, i. e., if the suspected material was of human origin, pre- 

 cipitation will occur in tubes I and VI, while II, III, IV, and V 

 remain clear. 



With this method reliable results can be obtained, so long as the 

 material under examination contains albumins w r hich are still cap- 

 able of undergoing solution, even though they be present only in 

 traces. Uhlenhuth and Beumer thus mention that they obtained 

 positive results with blood which had undergone putrefaction and 

 had been left exposed to the air for two years, as well as with dried 

 blood-stains which were more than fifty years old. 



FERMENT REACTIONS. 



The Pregnancy Test of Abderhalden. This test is primarily based 

 upon the observation that the parenteral introduction of complex 

 foodstuffs of alien origin either leads to the appearance in the blood- 

 serum of reaction products de novo which are capable of causing the 

 change of such bodies, or it increases the quantity of corresponding 

 products which may normally be present. Rabbit serum has thus 



