146 TYPHUS IN GUINEA-PIGS 



On the morning of October 28th the guinea-pig was found 

 lying upon its side, spastic, making incoordinated attempts 

 to arise. Its fur was in good condition, its eyes bright, but it 

 did not attempt to eat. It remained in this condition through- 

 out the day. It responded to handling by violent muscular 

 efforts. After etherization that evening the skeletal muscles 

 remained irritable long after the post mortem was completed 

 a phenomenon which we have seen frequently in rabid 

 animals. The post mortem showed a moderately enlarged 

 spleen, but no other definite lesions. The peritoneal surfaces 

 were normal. The stomach and intestines were empty. The 

 lungs, pleura, heart, and pericardium were normal. The brain 

 showed a marked injection of the superficial blood vessels. The 

 histological examination showed very extensive proliferative 

 lesions throughout the cerebrum and cerebellum, identical 

 with but much more numerous than those usually seen in 

 typhus guinea-pigs. 



3. GROSS PATHOLOGY IN GUINEA-PIGS 



The changes to be noted are slight. The skin is negative. 

 The inguinal and axillary lymph nodes are slightly enlarged, 

 never deeply injected, usually pale or at the most pink in color. 

 The peritoneal surfaces are normal. The spleen is usually 

 slightly to moderately enlarged and deeper red in color than 

 normal. The adrenal glands are occasionally moderately en- 

 gorged with blood. In male guinea-pigs a noticeable injection 

 of the testes and occasionally a small hemorrhage into the 

 polar fat has been seen. The scrotal tissues and tunica remain 

 normal and the reaction in our experience has been in no way 

 comparable to that of Rocky Mountain spotted fever in guinea- 

 pigs or as described with Mexican typhus by M. H. Neill 

 (1917). 



The brain is occasionally noticeably injected, but exhibits 

 no positive gross evidences of the lesions found microscopically. 

 The organs of the chest, liver, kidneys, and gastro-intestinal 

 tract show no lesions or alterations in appearance from the 

 normal. 



