10 PROPERTIES OF H^EMOLYTIC SERA 



lytic dose of immune-body are added to a number of tubes 

 in series : time is allowed for combination, and the tubes 

 are then centrif ugalized : the fluid from each is pipetted off 

 and added to the corpuscles of 1 c.c. of suspension (the salt 

 solution having been previously removed by centrifugaliza- 

 tion). Sufficient complement for lysis is then added to each 

 tube, and the tubes are incubated at 37 C. for two hours. 

 The quantity of immune-body left free, up to a complete 

 haemolytic dose, can thus be determined in the case of each 

 tube by the degree of lysis which occurs. The amount of 

 immune-body taken up by the corresponding red corpuscles 

 varies within very wide limits in different cases. Ehrlich and 

 Morgenroth found that in the case of one serum no more 

 than the haemolytic dose entered into combination ; that is, 

 if two haemolytic doses were added, one remained free in the 

 fluid, whereas in another case a hundred doses had to be 

 added before one dose remained free. In the case of rabbit 

 v. ox serum, I have found that the number of doses 

 estimated in this way varies from six to ten ; it is usually 

 seven or eight (variations seem to depend both upon the 

 serum in question and upon the corpuscles used in 

 testing). 



It is to be noted that the union of immune-body with the 

 haemolytic receptors of the red corpuscles is not like that 

 of a strong acid and base ; that is, there is not a sharp 

 neutralization point. Even when only two doses of immune- 

 body are added, an appreciable amount is found to be 

 left free in the fluid when it is separated, and with more 

 doses this gradually increases until a haemolytic dose is 

 free, as has already been indicated ; but when this stage is 

 reached the red corpuscles are not saturated. If X doses 

 give one free dose, more than X + 1 doses must be added 

 before two free doses are got. This is clearly brought 

 out in the adjoining table, which shows the amounts of 

 free immune-body when varying amounts of immune-body 



