SUBSTANCES WHICH ACTIVATE COBRA VENOM. 453 



respect the demonstration of lecithin in the stroma would appear to 

 be of special interest, for just this substance is regarded as particu- 

 larly important for the functions of the protoplasm. 1 



A further problem, to be sure, is whether this lecithin exists free 

 in the red blood-cells. We have a number of reasons for believing 

 that this is not the case. It was first shown that in yolk of egg 

 only a small part of the lecithin can be shaken out with ether, whereas 

 by extracting with alcohol the entire amount can be obtained. 2 The 

 reason for this is that the greater part of the lecithin is conjugated 

 with the vitellin of the yolk. This combination can be obtained 

 as a globulin-like body which is soluble in salt solution and precipitates 

 on dialyzing. 3 



The lecithin is obtained free, however, only after extraction with 

 alcohol, by which the vitellin also changes and becomes insoluble 

 in salt solutions. In demonstrating the presence of lecithin by 

 means of cobra venom we too have observed that the serum and the 

 red blood-cells yield no lecithin to ether, or if they do it is only in 

 faint traces. On the other hand, the active power of the alcoholic 

 extracts at once led to the recognition of the presence of lecithin. 



From this point of view some of our earlier observations can 

 easily be explained. We stated that solutions of certain species 

 of blood-cells were strongly activating, while others showed this 

 property to a far less degree or not at all. The alcoholic extracts 

 of all species of blood, however, contain nearly the same amount of 

 lecithin (demonstrated by the activation of the cobra venom). This 

 apparent contradiction is readily explained by the fact that in the 

 different species of blood the lecithin is conjugated with different 

 substances of the stromata and, furthermore, that the firmness of 

 this combination varies extensively. Thus in goat blood the union 

 is so firm that the avidity of the cobra venom does not suffice to 

 separate the two components; the consequence is that there is no 

 activation with a solution of goat blood. On the other hand, in 



1 It has long been known that lecithin is a constant constituent of the 

 red blood-cells; for many species of blood-cells this content has even been 

 worked out quantitatively. Nothing, however, was thus far known concern- 

 ing the localization of the lecithin. 



2 See Hoppe-Seyler's Handbuch der physiologisch- und pathologisch-chem- 

 ischen Analyse, Seventh Edition, edited by H. Thierfelder, Berlin, 1903, 

 page 157. 



8 Ibid. , page 369. 



