4 



Scientific Proceedings (50). 



3 (699) 



The importance of calcium in relation to growth. 

 By Francis H. McCrudden. 



[Rockefeller Institute Hospital, New York.] 



In certain cases of retarded development there is faulty 

 skeletal development and disturbed calcium metabolism. The 

 bones are frail and easily fractured; large quantities of calcium 

 are lost through the feces, and the urine is almost free from 

 calcium. It seems probable that the retarded skeletal develop- 

 ment is due to the lack of calcium salts available for bone growth. 

 Other cases of retarded development show no such disturbances 

 of calcium metabolism and the bones are of normal solidity. In 

 these cases there is a more fundamental absence of the "tendency 

 to grow" rather than any lack of material for growth. 



4 (700) 



The pyramid tract in the Canadian porcupine (Erethizon dorsatus 



Linn.). 



By Sutherland Simpson. 



[From the Physiological Laboratory, Medical College, Cornell Uni- 

 versity, Ithaca, N. Y.] 



The nerve fibers of the pyramid tract pass caudalwards from 

 their cells of origin in the motor area of the cerebral cortex and 

 are homo-lateral until the lower part of the medulla oblongata is 

 reached. At this level, in the majority of mammals that have 

 been examined, most of the fibers decussate and take up a position 

 in the lateral column of the spinal cord on the opposite side, just 

 ventral to the posterior horn, forming the crossed lateral pyramid 

 tract. A few fibers remain uncrossed and are found in the lateral 

 column on the same side, constituting the direct lateral pyramid 

 tract. 



In man and the anthropoid apes a second uncrossed tract is 

 found in the ventral column — the direct ventral pyramid tract. 

 In mammals lower in the scale than the anthropoids, it is generally 

 held that this direct ventral tract is not represented at all. 



