474 COLLECTED STUDIES IN IMMUNITY 



bility in ether and its ready solubility in water; from cobra venom 

 amboceptor in its solubility in the above-mentioned organic solvents, 

 alcohol, chloroform, toluol. Cobra venom does not give up even a 

 trace of cobra amboceptor to these solvents. 



It has been found that the watery solution of the primary cobra 

 lecithid obtained from cobra venom and lecithin, as described above, 

 undergoes spontaneous modification which leads to the formation 

 of an insoluble substance. If the watery solution is allowed to stand 

 at room temperature it gradually becomes cloudy, and in the course 

 of a few hours a whitish precipitate is formed. On removing this pre- 

 cipitate, either by filtration or by centrifuge, a precipitate will again 

 form in the clear fluid. The sediment is microcrystalline, white, trans- 

 parent, and very refractile. 



It can easily be shown that this sediment is nothing but a modified 

 form of the lecithid, for after thoroughly washing the precipitate 

 which has been separated by the centrifuge, it will be found that 

 this still exerts its full htemolytic action. In accordance with this, 

 the original solution of the primary product shows a proportionate 

 loss of power. In one experiment which we followed rather closely 

 we found that in course of time about two-thirds of the lecithid had 

 separated out in solid form, while one-third was still left in solution. 

 The secondary lecithid produced in this way is, as already stated, 

 almost insoluble in cold water; on the other hand, it is readily soluble 

 in warm water, although it again separates on cooling. This be- 

 havior constitutes the chief difference between the primary and the 

 secondary lecithid; the behavior of the two substances toward the 

 above-mentioned organic solvent is identical 



Owing to its character the secondary lecithid is particularly adapted 

 for chemical investigations, and one of the foremost authorities has 

 already commenced work on this substance. Some important results 

 which have already been obtained will be mentioned later on. For 

 the present we shall merely mention that the product gives no biuret 

 reaction even when in concentrated solutions. We are reserving for 

 future study the chemical study of the above lecithids, as well as the 

 investigation of the neurotoxin obtained in purified form by means 

 of the method above described. 



The formation of the secondary lecithid also occurs if the ethereal 

 precipitate is dried at incubator temperature. It is then easy to see 

 that such a product has more or less completely lost its solubility in 

 water, especially if it has remained in the thermostat for several days. 



