1) On the simplification of the splenic tissue culture, the author studied the influences of the various serums and growth promoting substances upon the splenic tissue culture of mice, rabbits and rats. 2) Culturing these spleens with the unactivated serum or untreated serum, the author concluded that the splenic culture with the unactivated serum was superior to the latter in all data of cultures. 3) Culturing these spleens by adding vitamin B(12), folic acid or nucleic acid, which were on the market, for the growth promoting substances, both in mice and rats the cultures adding vitamin B(12) showed comparatively excellent growth, and in rabbits the cultures adding folic acid or vitamin B(12) showed somewhat good growth, between which significant difference was not shown. 4) On the basis of these results we called the following method the clinical tissue culture method of the spleen, in which the spleen was cultured in the medium composed of unactivated serum and vitamin B(12) (100(γ)/(c.c.)) using the Hiraki's tissue culture slide No. 1, and then the data using this tissue culture method was compared with those obtained by the conventional plasma clot culture method. These results showed that, although this method was slightly inferior to the plasma clot culture method in the data of cultures, it was sufficiently fit for clinical application.