THE COMPARATIVE ANATOZMY OF THE 

 PYRAMIDAL TRACT 



A. J. LINOWIECKI 



F7-o)n the Anatomical Labcratury of the Northwestern University Medical School 



EIGHT FIGURES 



The pyramidal tract, fasciculus cerebro-spinalis or fasciculus 

 cortico-spinalis, has furnished a very interesting topic for investi- 

 gation on account of the variations in location of this tract in 

 the spinal cord. There are also interesting variations in the 

 size of the tract and in the size of its fibers. Of special interest 

 is the late medullation of the tract in man, and the failure of 

 medullation to complete itself in certain animals, as the rat 

 (Ranson) and mole (Draeseke). 



The principal object of this investigation was to determine 

 the degree of medullation in adult animals of various orders. 

 The work was undertaken at the suggestion of Prof. S. Walter 

 Ranson and carried out under his direction. 



The animals used were those which were readily obtained 

 and yet represented, as far as possible, different orders of the 

 Mammalia. The Rodentia were represented by the rat, rabbit 

 and guinea-pig; the Insectivora by the ground-mole; Carnivora 

 by the cat and the Primates by the monkey. 



REVIEW OF THE LITERATURE 



It has been repeatedly shown that the fasciculus cortico- 

 spinalis or the pyramidal tract in the ^Mammalia may lie in any 

 of the funiculi of the cord, that its size diminishes as it proceeds 

 caudalward, and that it often disappears upon reaching the 

 lumbar region. In the cords of the mouse, rat and guinea-pig, 

 this tract is found in the posterior funiculus of the cord; that in 

 the rabbit and in the Carnivora (Spitzka) is seen to traverse the 

 lateral funiculus; while in man it is located, in part, in the lateral 

 and in part, in the anterior funiculus (v. Lenhossek '89). 



509 



THE JOURNAL OP COMPARATIVE NEUROt.OOY. VOL. 24. NO. 6 

 DECEMBER, 1914 



