STUDIES ON CYTOLYSINS v 69 



less until cells of the kind used as antigen have been rendered 

 vulnerable by the action of the specifically generated immune 

 body. Even the complement in an animal's own serum will 

 suffice to dissolve one of its own tissues if the proper amboceptor 

 is introduced. 



Views as to just how these various elements combine and 

 react are nearly as numerous as the investigators who have 

 studied them. The explanation vouchsafed by the Ehrlich 

 school for the lack of absolute specificity, is that certain of the 

 different tissues of the body have receptors of the same kind, 

 so that anyone of such a group of tissues might serve as an 

 antigen for all the others. In other words, according to them, 

 specificity is not a matter of cells, but of receptors. 



There is urgent need for further investigation of cytolysins 

 not only as regards this question of tissue specificity, but also 

 as to the degree of specificity or lack of specificity for the ho- 

 mologous tissues on groups of related organisms. Furthermore, 

 cytolysins have been developed so far for only a very limited 

 number of tissue elements. The reports of pathologists who are 

 seeking to develop specific cytolytic sera for cells of pathological 

 origin, particularly malignant tumors, are increasingly discourag- 

 ing, since apparently the distribution of common receptors is too 

 widespread to permit the formation of antisera with sufficient 

 specificity for medical purposes. But this difficulty need not 

 block the biologist in his efforts to secure certain other results. 



If it is possible to originate in living organisms antibodies 

 which will destroy particular tissue elements, is it not possible 

 to secure similar selective action on certain parts of the de- 

 veloping embryo? Moreover, if we are ever to break through 

 the apparent impass which has enveloped our long-standing 

 problem of the inheritance of somatic modifications, or that 

 of provoking specific modifications in the germ through direct 

 operation of external agencies, is not the employment of cyto- 

 lysins possibly a line of attack which may yield fruitful re- 

 turns? If a special serum will single out and destroy a certain 

 element of the adult, is it not possible that there is sufficient 

 constitutional identity between the mature substance of that 



