No. 630] FAMILY RELATIONSHIP 



47 



ished; fibroblasts are given freer access to the trans- 

 plant, and moreover, the fibroblasts undergo secondary 

 changes ; they form fibrous tissue, while after allotrans- 

 plantation the cytoplasm usually remains to a much 

 greater extent intact without undergoing the secondary 

 changes in contact with the grafted cells. 



These toxic substances not only interfere with those 

 proliferative processes which are of a regenerative char- 

 acter in the more restricted sense, but also with others 

 caused by growth substances; thus they interfere with 

 the production of experimental deciduomata in the 

 uterus or with compensatory hypertrophy of the thyroid 

 after homoiotransplantation, without however neces- 

 sarily preventing these growth processes entirely. Ulti- 

 mately they endanger the life of the exposed tissues, 

 usually indirectly through the action of the lymphocytes 

 and connective tissue cells, more rarely directly. 



Furthermore the syngenesio-, homoio- and hetero-dif- 

 ferentials may act secondarily as antigens directly or 

 after interaction with the body fluids and then call forth 

 the production of immune substances. Such immune sub- 

 stances however in most cases become demonstrable only 

 if the strangeness of the antigen used has been very 

 marked; this is for instance the case if a hetero-differen- 

 tial serves as an antigen (Schoene, M. S. Fleisher). A 

 homoio-differential is only in some cases able to become 

 an antigen. Under certain conditions homoio-haemoly- 

 sins can appear (Ehrlich and Morgenroth) or haemag- 

 glutinins (von Dungern and Hirschfeld) and further- 

 more homoio-immune substances can be produced against 

 growing tumors and embrvonal tissues (Fichera, Pevton 

 Rous). In the case of tumor immunity lymphocytes play 

 a very prominent part. This has been noted by a num- 

 ber of investigators. More recently the significance of 

 lymphocytes in immunity has been demonstrated in 

 varied experiments especially hv J. B. Murphy and his 

 collaborators. However, as we shall see presently, the 

 direct reaction of tissues (including lymphocytes) against 

 syngenesio-, homoio- and heterotoxins is a finer bio- 



