SEVENTH ANNUAL REPORT. 113 



of the diseased area are surrounded by a pronounced infiltration 

 of small round and occasional plasma cells, and many of them 

 are completely occluded by fibrous tissue which has developed 

 about them, chiefly in the adventitia. 



"Groups of the Mischerschen Schleuche are frequent in the 

 muscle cells, and a few are found in the fibrous tissue, apparently 

 remaining after absorption of the muscle cells in which they were 

 originally lodged." 



Apparently this aneurism of the heart was formed by degen- 

 eration of the muscle cells in this particular area, probably pri- 

 marily due to the presence of the Mischerschen Schleuche, with 

 fibroid replacement of the muscle tissue as degeneration pro- 

 gressed. It is also probable that the condition was favored by 

 the inflammation which may accompany the encystment of the 

 schleuche. It is possible, however, that the original lesion was 

 thrombosis of the left coronary artery with consequent muscular 

 degeneration and fibroid replacement. This is the more common 

 cause of aneurism of the heart in the human. In so far as I am 

 able to learn, this case is absolutely unique. 



MUSCULAR ATROPHY. 



One of the most remarkable specimens obtained during the 

 past year was that of a beaver, which showed very pronounced 

 atrophy of the muscles of the rear extremities. The character 

 of the lesions in this case differs entirely from those of ordinary 

 muscular atrophy, and its causation is a complete riddle to us. 

 No history was, of course, obtainable, and unfortunately neither 

 the spinal cord nor the peripheral nerves were secured for ex- 

 amination. 



DEATH FROM INJURIES. 



Fortunately, the number of deaths from injury has been very 

 small. This is a most excellent showing, especially where so 

 large groups of animals are kept together as is the practice with 

 us. But eight deaths resulted frorn this cause. 



CAUSE OF DEATH UNKNOWN. 



We have been able to establish the cause of death in all re- 

 corded cases except four. In this regard I must especially com- 

 mend the industry and thoroughness of Dr. Blair, to whom the 

 major part of this work has been entrusted. 



