278 FRANK C. MANN AND DELLA DRFPS 



eosin, Mallory's connective-tissue stain and a few other special 

 stains such as Scharlach R. 



The structure of the spleen of the spermophile does not differ 

 essentially from that of the spleen of other rodents. The splenic 

 nodules are prominent and the sinuses rather large. The most 

 notable fact in regard to the histology of the organ is the rela- 

 tively thick trabeculas containing a large amount of smooth 

 muscle. In the gland of the active animal usually only a small 

 amount of blood is found. 



A^ithin twelve hours after an animal becomes torpid the spleen 

 presents a very characteristic appearance. Grossly and micro- 

 scopically the organ is markedly congested. It is greatly en- 

 larged and much darker in color than normal. The capsule 

 is tense and the tissue friable. On section an increased amount 

 of dark blood escapes. Owing to the large amount of blood pres- 

 ent it is impossible to recognize any of the finer detfiils of the 

 organ grossly. Microscopically the organ presents a most in- 

 tense congestion. The sinuses and venous capillaries are dis- 

 tended to their fullest extent with blood. In some organs red 

 corpuscles were found in the germ centers. It appeared as if 

 the congestion was so great as to force the cells into these 

 centers. 



The hibernating spleen reaches its maximum state of con- 

 gestion within a few days after the animal becomes torpid and 

 maintains this condition until after about forty days of hiber- 

 nation. After the animal has been torpid for seventy-five days 

 the amount of blood contained in the spleen is not greatly in 

 excess of that found in the organ of the active animals. The 

 blood seems to begin to decrease at the periphery of the organ 

 first. This is probably due to the fact that the effect of the con- 

 traction of the intrinsic muscles is first exerted on the surface of 

 the organ. 



Besides the marked congestion there seems to be very little 

 other change in the spleen. In some animals which had been 

 torpid for many days there seemed to be a slight proliferation 

 of the connective tissue, especially around the splenic nodules. 

 Specimens of the spleens of both active and torpid animals were 



