TRANSPLANTATION OF TISSUES IN MICE 57 



fibrous tissue in cases in which grade 1 was given, or variable parts were pre- 

 served ; in the latter case, the transplant was stunted, even if an almost com- 

 plete chain of acini was found in a fibrous nodule. Lymphocytes could be lack- 

 ing in such grafts, but in other instances some collections of lymphocytes 

 were found in certain places ; the dense masses of lymphocytes, which oc- 

 curred so often in rat and guinea pig, were as a rule absent in the mouse. The 

 transplanted striated muscle was either wholly necrotic or small numbers of 

 regenerated muscle fibers filled with nuclear chains could be seen. In the 

 muscle likewise, some lymphocytes could accumulate. The average grade in 

 these ten transplantations corresponded to 1 + . 



We have carried out in addition, several other large series of experiments, 

 in which at different times, extending over a number of years, we determined 

 the mode of reaction in the reciprocal exchange of tissues between the fol- 

 lowing inbred strains of mice: A, D, C3H, CBA, C57, Old Buffalo, New 

 Buffalo, C, and AKA. A detailed discussion of these experiments will not be 

 undertaken, but a brief statement of the principal results may be made. The 

 examination took place, as a rule, between 12 and 30 days following trans- 

 plantation ; injurious effects, on the average, increased with increasing time 

 of exposure to the bodyfluids and cells of the host. The grades were changed 

 correspondingly. After 20 and 30 days, they varied in the majority of cases 

 between 1 and 2— ; but in some cases the grades were slightly higher than 2 — , 

 without however definitely reaching 2. Intra-strain transplantations, which 

 were carried out at the same time, yielded higher grades. There was quite 

 generally a correspondence between the state of preservation or injury of the 

 various tissues in individual experiments. However, this did not necessarily 

 involve a correspondence in the degree of lymphocytic infiltration, because the 

 latter was often determined by local factors, among which, perhaps, local in- 

 fection with bacteria played a role in a number of cases. While lymphocytes 

 were by no means present in all homoiotransplants of cartilage and fat tissue, 

 some increase in connective tissue and infiltration of the fat tissue with small 

 vacuolated phagocytic cells was the most frequent indication of the incom- 

 patibility between the homoiogenous hosts and transplants. The lymphocytic 

 infiltration cannot serve, therefore, as an indicator of the relationship between 

 the individuality differentials of host and donor in the mouse to the same 

 extent as in guinea pig and rat. 



We have, thus, in these inter-strain transplantations, to deal with marked 

 homoio-reactions similar to those found in transplantations of homoiogenous 

 tissues in rats and guinea pigs. They differ from the latter in the decidedly 

 decreased invasion of the grafts by lymphocytes and by connective tissue, in 

 the frequent preservation of a stunted thyroid, in which lymphocytic infiltra- 

 tion was absent, and in the usually much diminished organizing activity of the 

 connective tissue. As in the case of the rat, so also in the mouse the muscle 

 fibers which were transplanted with xiphoid cartilage and fat tissue were 

 relatively more resistant than the bone marrow, which was invariably de- 

 stroyed in these homoiotransplants. Also, in the mouse the perichondrium 

 was able to regenerate new cartilage, but the connective tissue cells seemed 



