Life and Growth of Transplanted Tissues. 153 



the refractive index, the percentage of total proteins and the 

 relative amount of globulins of the sera showed little or no ten- 

 dency to drop below their original values. When the Wassermann 

 reaction, on the other hand, became very readily negative the 

 curves fell progressively and fairly rapidly during the course of 

 injections. 



The writer is indebted to Dr. John A. Kolmer and Dr. Jay F. 

 Schamberg for the laboratory and clinical facilities of the Derma- 

 tological Research Laboratories and the Polyclinic Hospital 

 which they kindly placed at his disposal. Special acknowledge- 

 ment is due to Dr. Charles Weiss of the D. R. Laboratories who 

 compiled and interpreted the data and prepared this manuscript 

 for publication. 



74 (1656) 



The analysis of factors which determine the life and growth of 

 transplanted tissues. 



By LEO LOEB. 



[From the Department of Comparative Pathology, Washington 

 University School of Medicine, St. Louis] 



1 . We may distinguish between two sets of factors determining 

 the fate of transplants: (a) primary or constitutional; (b) secon- 

 dary or extraneous factors. The former comprise the individuality 

 and species differentials, and possibly organ specific factors; the 

 latter include such factors as age, sex, pregnancy, infection and 

 immunity. There are in addition general factors as oxygen 

 supply, character of circulation and temperature; the latter we 

 shall at present leave out of consideration. 



If we take the subcutaneous transplantation of the thyroid 

 gland as type, we find the following variables which may be 

 influenced by the two sets of conditions: (a) the amount of sur- 

 viving parenchyma and its growth energy; (b) the behavior of 

 the connective tissue cells; (c) of blood and lymph vessels, and 

 (d) of the lymphocytes of the host towards the transplant. 



2. In a series of earlier papers we have analysed the effect of 

 the individuality and species differentials on these four variables 



