THE PYRAMIDAL TRACT 519 



The medullated fibers were found to be of greater diameter than 

 those found in the rat, and the largest measured 12.58At in di- 

 ameter. The largest fibers in the guinea-pig cord probably are 

 admixtures from the fasciculus cuneatus. Most of the medul- 

 lated fibers measure from 1.39m to 4.84 /z in diameter. 



Rabbit 



The spinal cord of the rabbit does not stain well by the p>Tidine 

 silver method. The results are improved by a preliminary 

 injection of 2 per cent ammonia in 95 per cent alcohol (Hubert . 

 This fixed the cord 'in situ' and increased the sharpness of the 

 staining. The area occupied by the pyramidal tract is indicated 

 in figure 3. It is located in the lateral funiculus close to the 



Fig. 3 Diagram of the cervical cord of the rabbit according to v. Lenhossck, 

 showing the position of the pyramidal tract. 



columna posterior and near the periphery of the cord (v. Len- 

 hossek). The tract is not sharply outlined in pyridine-silver 

 preparations but the area which it occupies is somewhat more 

 darkly stained than the rest of the white substance. 



V. Lenhossek ('89) says that the tracts occupy, approximately, 

 the posterior third of the lateral funiculus in the upper cervical 

 region and at the level of the middle cervical part, the tract 

 occupies 5.3 per cent of the cross-section area of the cord. In 

 the words of this investigator, the tract is located as follows: 



Im cervical Teil erkennt man Folgendes: Das marklose Gebiet 

 iiimmt den hintersten Teil der Seitenstriinge ein. Hinten grenzt es 



1 Observations on the peripheral distribution of the nervus terminalis in 

 Mammalia. Anat. Rec, vol. 7, p. 253, 1913. 



