412 S. WALTER KANSON 



liope to follow it with a comparative study of the pyramidal 

 fibers in several different orders of mammals. For this reason 

 no attempt will be made at this time to give a comprehensive 

 review of the literature. 



Stieda ('69) noticed that the pyramidal tract in the mouse 

 occupied the posterior funiculus. Spitzka ('86) showed that this 

 position was characteristic for the rat and the guinea-pig. These 

 observations were confirmed on the rat by Von Lenhossek ('89) 

 and Bechterew ('90), using the embryological method of Fleich- 

 sig. Further confirmation was obtained through the application 

 of the Marchi stain to the degenerating tract in the rat by Gold- 

 stein ('04), Van der Vlort ('06) and Miss King ('10). 



TECHNIQUE 



In this investigation the pyridine-silver (modified Cajal) tech- 

 nique (Ranson '12) was used as the principal method and the 

 results were controlled by the use of the Weigert and the Pal- 

 Weigert methods. For the Weigert methods some of the cords 

 were fixed in Mtiller's fluid and others after fixation in 10 per 

 cent formahn were mordanted either in Mtiller's fluid or in the 

 following solutions: 



Primary mordant 



Bichromate of potassium 5.0 grams 



Fluorchrom 2.0 grams 



Water, ad 100.0 cc. 



Secondary mordant 



Acetate of copper 5.0 grams 



Acetic acid (35 per cent) 5.0 grams 



Fluorchrom 2.5 grams 



Water, ad 100.0 cc. 



The usual staining and differentiating solutions were employed 

 and paraffin as well as celloidin sections were utilized. An effort 

 was made to use as many different combinations as possible, and 

 in this way to exclude the possibility that the characteristic 

 staining of the pyramidal tracts was due to the particular modifica- 

 tion of the method employed. 



