THE PYRAMIDAL TRACT 525 



interrupt this fissure near its anterior end, then it would bisect 

 the fissure, as seen in figure 7, and finally it would be seen near 

 the anterior commissure, the septum extending almost through 

 the entire field. This process would repeat itself after an interval 

 of two or three consecutive sections in which no axons were seen 



A 





.CC. 



.c a 



Fig. 7 From a section taken somewhat below the middle of the cervical 

 portion of the spinal cord of the mole (Scalopus aquaticus). Pyridine silver. 

 X 93. Compare with figure 6 and note the rapid decrease in the size of the tract 

 as it is traced caudalward. A bridge of decussating fibers unites the two tracts 

 across the anterior median fissure. The marked flattening of the anterior surface 

 of the cord is a distortion produced when the cord was removed. 



in the path of the anterior median fissure. This succession of 

 bands of decussating fibers extending across the anterior median 

 fissure and separated by open intervals was found to be coex- 

 tensive with the pyramidal tract and to cease at the lower level 

 of the cervical cord with the termination of the pyramidal tract. 

 These observations seem to indicate a decussation of the 

 pyramidal tract in the cervical portion of the spinal cord. 



A study of serial sections of the entire cervical cord of the mole 

 shows that the size of the tract decreases rapidly as it runs 



THE JOURNAL OP COMPARATIVE NEUROLOOY. VOL. 24, NO. 6 



