324 Wassermann Reaction for Diagnosis of Syphilis 



from the carotid artery, according to the directions given in 

 the chapter upon Experiments upon Animals. 



The blood thus obtained is permitted to coagulate, and the 

 serum, which should be clear, removed with a pipet. More 

 serum may be obtained from the clot by cutting it into strips, 

 placing these in a centrifuge tube, and whirling them for 

 fifteen minutes. 



Having thus described the preparation of the reagents to be 

 employed in making the Wassermann test, the next step, that 

 of titrating them, becomes essential. One of the first ques- 

 tions that presents itself is how successful titration of reagents 

 that may all be more or less variable can be effected. To 

 achieve this it is necessary to begin with those that can be 

 assumed to present the least variation and work up those that 

 are most variable. 



(1) The Sheep Corpuscles. As these come from a healthy 

 animal, are always treated in precisely the same manner and 

 used under standard conditions of freshness, they can be 

 looked upon as an invariable factor : i c.c. of the 5 per cent, 

 suspension forms a good working quantity and constitutes 

 I unit. 



(2) The Normal Guinea-pig Serum Containing the Comple- 

 ment. As this also comes from a normal animal, is always 

 treated in precisely the same manner, and is also used under 

 standard conditions of freshness, etc., it may also be looked 

 upon as a factor subject to very slight variation. Of this 

 serum, o.i c.c. (i c.c. of a i : 10 dilution) forms the unit, 

 or working quantity. 



These two reagents, therefore, may be regarded as the 

 standards of measurement through which the titer of a 

 third is made possible. 



(3) The hemolytic serum from the rabbit treated with the 

 sheep corpuscles. 



This is subject to very great variation, according to the 

 treatment of the rabbit, and apparently, also, according to 

 the ability of the individual rabbit to respond to the treat- 

 ment by the formation of hemolytic amboceptors. It is, 

 therefore, imperative to make a careful titration of this 

 reagent. 



To do this we proceed as follows, the quantities recom- 

 mended being such as experience has proved most satis- 

 factory : 



Into each of a series of common test-tubes or culture- 



