The Blood-corpuscles 283 



time, the clot, as soon as formed, may be cut into strips and placed 

 in the tubes of a centrifuge and whirled for a half -hour. This se- 

 cures a greater quantity of the serum and at the same time gives it 

 its full value, probably by injuring the leukocytes. 



Such serum containing the complement is useful for twenty-four 

 hours. Longer it should not be kept or used, as it begins to deterio- 

 rate almost at once, and the deterioration increases in rapidity in 

 proportion to the length of time it is kept. The quantity of the com- 

 plement in the serum of the guinea-pig is fairly constant, when the 

 animal is regularly fed, and furnishes a fairly uniform reagent that 

 requires no titration. 



II. For the second, or hemolytic, test two additional reagents 

 are required: 



Blood-corpuscles to be dissolved. 



Hemolytic amboceptors by which complement may be 

 united to them. 



(4) The Blood-corpuscles. It makes no difference what kind of 

 blood-corpuscles are employed. Ehrlich and Morgenroth, in their 

 pioneer experiments into the mechanism of hemolysis, used goat 

 corpuscles. Bordet used rabbit corpuscles; Wassermann, Neisser, 

 and Bruck, sheep corpuscles; Detre, horse corpuscles; Noguchi, 

 human corpuscles. 



As those who do many tests require a considerable quantity of 

 blood, it seems wisest to make use of some kind that is readily ob- 

 tainable in any quantity, hence most investigators now follow 

 Wassermann and his collaborators and use sheep blood, which is 

 easily obtained at a slaughter-house or from sheep kept for the 

 purpose. 



The flowing blood is caught in some open receptacle, stirred until 

 it is defibrinated (it must not be permitted to coagulate), and then 

 taken to the laboratory. 



The corpuscles must next be washed with care, so as to free them 

 from all traces of amboceptors and complement belonging to the 

 serum in which they are contained. For this purpose a centrifuge 

 is indispensable. The tubes of the apparatus are filled with the 

 defibrinated blood and then whirled for fifteen minutes until the 

 corpuscles form a compact mass below a fairly clear serum. The 

 serum is then cautiously removed and replaced by 0.85 per cent, 

 sodium chlorid solution, the top of each tube closed by the thumb, 

 and vigorously shaken so as to distribute the corpuscles throughout 

 the newly added fluid. The tubes are next returned to the centrifuge 

 and again whirled until the corpuscles are sedimented, when the 

 fluid resulting from this first washing is removed and replaced by 

 fresh salt solution, in which the corpuscles are again thoroughly 

 shaken up. They are now again whirled until again sedimented, 

 when the second washing is removed, leaving the corpuscular mass 

 undisturbed. Some prefer to give the corpuscles a third washing, 



