340 COLLECTED STUDIES IN IMMUNITY. 



For many years, owing to the valuable researches of Buchner, 

 an inactivation by means of temperature of 55-56 was regarded 

 as practically a specific criterion for the alexins. We now know, 

 however, that no general rule can be formulated in this respect. On 

 the one hand there are complements which are not at all influenced by 

 the customary half-hour's heating to 55 C. (thermostable comple- 

 ments), and on the other there are amboceptors which are com- 

 pletely destroyed by such heating. A complement belonging to the 

 first category was first described by Ehrlich and Morgenroth 1 as 

 occurring in considerable amount in normal goat serum and in the 

 serum of a buck which had been immunized with sheep serum; and 

 thermolabile amboceptors, especially in normal sera, are not at all 

 rare. Thus the amboceptor above mentioned regularly present in 

 horse serum and acting on guinea-pig blood, as well as one studied 

 by Sachs 2 present in dog serum and also acting on guinea-pig blood, 

 is completely destroyed by half an hour's heating to 55 C. Hence 

 the first rule in the demonstration of the complex character of hsemo- 

 lytic poisons by thermogenic inactivation is always to employ the 

 lowest temperature at which inactivation takes place within a short 

 time (20-60 minutes). 3 



VI. The Quantitative Estimation of Amboceptors, Complements 



and Receptors. 



In special cases, e.g. during the course of an immunization, 

 it is of considerable value to accurately determine the amounts of 

 amboceptor and complement present in the serum. While referring 

 to the studies of v. Dungern (p. 36), Bulloch (I.e.), Morgenroth and 

 Sachs (pp. 226 and 250), we should like to emphasize that, in general, 

 in determining the amount of complement it is necessary to make 



1 See page 13. 



2 See page 181 et seq. 



3 According to the researches of Korschun and Morgenroth (see pp. 267 

 et seq.) the haemolytic substances of organ extracts are "coctostable," i.e., 

 they are not destroyed even by several hours' boiling. Hence we designate a 

 substance as 



Thermolabile, if it is rendered inert by heating to 55-56 C.; 



Thermostable, if it withstands heating to 56 or over but is destroyed by 



boiling; 



Cortostable, if it resists boiling at 100 C. 



In special cases in order to still more closely characterize their behavior 

 one can add temperature and duration of heat as an index. 



