It is well known that the serum of cancer pationt possesses a specific coagulability to heat. By estimating heat-resistant non-coagulating substances of the serum in the rabbits previously injected with cancer tissue extract and benign gastric mucosa extract by Tsuda-Okujima's method the author pursued changes in these substances as well as inves tigated the relationship between the erythrocyte count, leucocyte count, and plasma protein content. The following are the results. 1. Rabbits given intravenous injection of cancer tissue extract to the ear-lobe show marked differences from those similatly injected with benign mucosa extract. 2. Observation for a long period of time is possible when extract is given intraperitoneal, and those injected with cancer tissue extract show a marked increase in heat-resistent non-coagulating substances when compared with those injected with benign mucosa extract. 3. There is a certain relationship between the change of the erythrocyte count and that of the hemoglobin content, namely, between the degree of anemia and the change of heatresistant non-coagulating substances in serum, but in the strict sense it is not a parallel relationship. 4. Between the leucocyte count and heat-resistant noncoagulating substance not any relatinoship can be recognized. 5. No completely parallel relationship can be recognized between the plasma protein content and heat-resistant noncoagulating substance. 6. Likewise no parallel relationship can be seen between tyrosine excreted in urine and heat-resistant non-coagulating substance.