MODIFICATION OF REACTION OF THE HOST 181 



heterogenous transplantation of thyroid from rat to guinea pig, living acinar 

 tissue was found in two cases 10 days, and in two other cases, 18 days after 

 transplantation; there was formation of hyaline connective tissue in and 

 around these heterogenous transplants, and in some instances polymorpho- 

 nuclear leucocytes collected around them. At dates later than 18 days, the 

 transplants had disappeared. In this case, also, the results were somewhat 

 better than in heterogenous transplantations into the subcutaneous tissue. 



If we compare with these results, those obtained after intra-ocular trans- 

 plantations of malignant tumors, the latter are much more striking. In a 

 number of instances it has been possible to obtain active, continued growth in 

 the anterior chamber of the eye, where none was found subcutaneously, and 

 even heterogenous tumors, including human tumors, grew, in contrast to the 

 subcutaneous grafts of this tissue. The difference between the growth of 

 tumors obtained in these two sites is much greater than that of normal adult 

 tissue. Results of this kind have been recorded by Smirnova, by Greene, by 

 Greene and Saxton, by Appel, Saphir, Janota and Strauss, and by Cheever 

 and Morgan; but Greene found that not all heterogenous tumors could be 

 successfully transplanted into the eye; and the degree of success seemed to 

 depend upon the original growth energy of the tumor used for transplantation. 

 In some instances, also serial transplantations in the eye were successful. 

 After retransplantation to the subcutaneous tissue, of tumors that had grown 

 in the eye, the tumor cells died. The greater power of survival and growth of 

 tumors in the anterior chamber of the eye as compared to that of ordinary 

 tissues is in part probably due to the greater growth momentum inherent in 

 tumors, which leads to a multiplication of the advantages offered by conditions 

 in this site as compared with those present in the subcutaneous tissue. How- 

 ever it is possible that still another factor is active, namely, the diminution 

 or lack of immune substances in this region. Tumors, as a result of their 

 growth in hosts bearing different individuality differentials, as a rule seem to 

 give rise to immune processes to a higher degree than do normal tissues, per- 

 haps at least partly on account of their increase in mass, which takes place 

 with relatively great rapidity, and tumors are very sensitive to the injurious 

 action of such substances, especially during the first period following trans- 

 plantation. In the case of ordinary tissues, as we have seen, the primary 

 homoio- and heterotoxins are apparently very much more important in the 

 determination of their fate after transplantation than are the immune sub- 

 stances, although the latter may play some role also ; however, in the case of 

 tumors there is evidence that though the primary homoio- and heterotoxins 

 likewise help to determine the result after transplantation, the immune sub- 

 stances are of much greater consequence. But it has been shown by Becht 

 and Greer, and by Hektoen and Carlson, that the titer of immune substances 

 is much less in the fluids of the anterior chamber of the eye than in the 

 blood, or it may be lacking altogether in the former when it is present in 

 the latter region; and more recently, Appel, Saphir, Janota and Strauss 

 have stated this to hold good also for immune substances produced by 

 the growth of the Brown-Pearce tumor in rabbits. This condition would help 



