SPIROCH^TiE 383 



drawn from the carotid artery, allowed to clot and the serum 

 separated by standing at 37° C. for two to five hours. The clear 

 serum is transferred to small glass ampoules in amounts of 0.5 to 

 i.o c.c. and hermetically sealed. These are then heated at 56° C. 

 for 30 minutes and stored in the refrigerator. The hemolytic 

 power of this serum is ascertained by titration. The unit is that 

 amount which, when mixed with 0.2 c.c. (i unit) of corpuscles 

 and 0.1 c.c. (i unit) of complement and sufficient salt solution 

 (0.9 per cent) to make a total volume of i c.c, will cause complete 

 laking of the red blood cells in exactly i hour after being placed 

 in the incubator (water bath) at 37° C. The unit of amboceptor is 

 ordinarily contained in o.i c.c. of adilution of i part of serum in 

 500 to 1200 parts of salt solution. After the strength has been 

 ascertained by trial of a series of different quantities of a strong 

 (i :20o) solution, the amboceptor dilution to be used on the same 

 day is made up so that o.i c.c. contains i unit. 



*The amboceptor is quite permanent under ordinary refrigera- 

 tor conditions, but when diluted it may deteriorate after a few 

 days. The relation of complement, red blood cells and ambo- 

 ceptor is tested always immediately before undertaking a comple- 

 ment-fixation test. If the mixture of one unit of each of these in 

 a total volume of i c.c. produces' complete hemolysis at the end 

 of an hour, the hemolytic system is considered satisfactory. If 

 there is only a slight discrepancy this may be corrected by altering 

 the final dilution of the amboceptor from its usual strength, within 

 limits of 25 per cent. If the discrepancy is greater than this it is 

 well to obtain a new sample of complement or of sheep's cells or 

 of both. The hemolytic system should behave much .the same 

 from day to day when the technic is accurate. 



4. The patient's serum is obtained from 5 to 10 c.c. of blood 

 drawn from the elbow vein. The serum should be removed from 

 the clot within 24 hours, freed from corpuscles and preserved with 

 chloroform unless it can be tested promptly. Particular care is 

 required when the serum is to be sent by mail. The serum is 

 heated at 54° to 56° C. for 30 minutes just before use. 



