2S6 IMMUNOLOGICAL METHODS OF DIAGNOSIS 



All examinations are conducted in little test-tubes, such as those 

 used in the Wassermann work, which must, of course, be scrupulously 

 clean. Or, if very small amounts of material only are available 

 for the examination, this is conducted in glass capillaries. The 

 turbidity then develops at the zone of contact between the two 

 fluids, and may be advantageously observed with the aid of a 

 magnifying glass. 



PREPARATION OF THE SUSPECTED MATERIAL. This is brought 

 into solution with the aid of 0.85 per cent, saline, and is then further 

 diluted to such a degree that on boiling a small amount (1 c.c.) with 

 a drop of 25 per cent, nitric acid a slight opalescence develops. This 

 would correspond to a 1 to 1000 dilution of the blood in its original 

 state and represents the minimal degree of dilution (i. e., the 

 maximal concentration) with which the actual test should be made. 



The solution of the suspected material should, of course, also 

 be perfectly clear, to which end it may be necessary to pass it 

 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. Tube 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) corre- 

 sponding 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, precipi- 

 tation 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 



