118 THE BIOLOGICAL BASIS OF INDIVIDUALITY 



planted into a frog for only a few hours and then re-transplanted into a 

 mammalian host, large collections of polymorphonuclear leucocytes are at- 

 tracted by it and then destroy the transplant, likewise suggests this interpre- 

 tation. Similar is the result if pigeon skin is transplanted for various periods 

 into the frog and then re-transplanted into the guinea pig. That necrosis as 

 such, even necrosis of fat tissue, cannot be responsible for the accumulation 

 of such cells in or around the transplant is shown by the observation that 

 in rat and guinea pig, as well as in pigeon and chicken, necrotic areas do not 

 noticeably attract polymorphonuclear leucocytes if the necrosis develops in 

 homoiotransplanted tissues. And even in the mouse there are many homoio- 

 transplants entirely free from leucocytic infiltration. 



Various considerations, however, make it seem more likely that these cell 

 accumulations are due to heterotoxins, which are given off by the graft and 

 which diffuse into the surrounding tissue, especially after the graft has 

 become necrotic. We must then assume that there are chemical differences 

 between the necrotic areas in homoiogenous and in heterogenous tissues, 

 which are responsible for the different modes of reaction of the polymorpho- 

 nuclear leucocytes, and that the latter are attracted by either necrotic or living 

 tissue, in contrast to homoiogenous tissues, which do not attract them, although 

 a few isolated leucocytes may be found here also in the first few days follow- 

 ing transplantation ; however, the possibility cannot as yet be entirely excluded 

 that the growth of microorganisms is promoted by conditions present in the 

 heterotransplants, as compared to those in auto- and homoiotransplants, or 

 that both these factors — microorganisms and heterotoxins — may be active. 

 That a greater strangeness of the individuality differentials of host and graft 

 may favor the accumulation of bacteria is shown especially in mice; when 

 transplants come from nearly related donors, the collections of polymorpho- 

 nuclear leucocytes usually remain localized at one spot, while similar collec- 

 tions in transplants from further distant donors often affect the transplanted 

 piece as a whole, or at least over wider areas. As we have seen in the preceding 

 chapter, together with the leucocytes, also connective tissue, lymphocytes, 

 and, in the case of the fat tissue, small-vacuolated phagocytic cells, invade the 

 homoiotransplanted mouse tissue. In our laboratory several experiments have 

 been made for the purpose of deciding between the various possibilities re- 

 garding the appearance of polymorphonuclear leucocytes and some associated 

 conditions. 



1. Siebert exposed, in the water bath, the thyroid and cartilage, with ad- 

 joining fat tissue, of rats to temperatures ranging from 43° to 51°, for from 

 15 to 45 minutes, and then transplanted these pieces into guinea pigs; exami- 

 nation took place after 20 days. The activity of lymphocytes and polymorpho- 

 nuclear leucocytes was only slightly decreased and the connective tissue reac- 

 tion was even somewhat increased as compared with that observed in tissues 

 not previously heated. We interpret these results as indicating that heteroge- 

 nous tissues, even if they are killed through heating previous to transplanta- 

 tion, still possess and give off their specific heterotoxins to almost the same 

 extent as the unheated tissues. When the same procedure was used with 



