39^ "Journal of Comparative Neurology and Psychology. 



simply to give some demonstrations of the relation of the medul- 

 lated fiber to its cell of origin. These are taken from preparations 

 which were made by means of modifications of the Weigert-Pal 

 method which have so far proved rather uncertain and limited in 

 their applicability but are nevertheless here given. 



The material used was the lumbar cord of an infant five weeks 

 old. This had been previously fixed and preserved in lo per cent 

 formalin (4 per cent formaldehyde). Pieces about five mm. long 

 were placed in a neutral developer (ortol without alkali being the 

 one actually used) for two days and then transferred to copper 

 bichromate,^ 2 to 3 per cent for two days. They were then dehy- 

 drated, embedded in colloidin and cut. The sections were stained 

 in one per cent aqueous haematoxylin solution, twelve to twenty- 

 four hours, and decolorized with potassium permanganate and 

 weak sulphurous acid in the usual way. 



A variation consisted in a repetition of the mordanting. The 

 pieces of cord were treated as follows: Ortol, 3 days; copper 

 bichromate, i day; ortol, 4 hours; copper bichromate, i day; 

 ortol, 4 hours; copper bichromate, i day; dehydrated, embedded, 

 and cut; and sections stained and decolorized as before. 



Another variation consisted in staining the sections in Dela- 

 field's haematoxylin instead of an aqueous solution of haema- 

 toxylin. These were decolorized as before, the decolorization 

 taking place more rapidly. This variation gave the results some- 

 what different from the first two, as noted below. 



Those who have worked with the Weigert-Pal method and its 

 various modifications are aware of the tendency at times for some 

 of the bodies and coarser dendrites of the nerve cells to remain 

 undecolorized. This tendency is usually more pronounced when 

 sulphurous acid is used instead of the oxalic acid-sulphite mixture 

 originally recommended by Pal. It may be diminished by adding 

 potassium chlorate to the mordant, at least when formalin material 

 is mordanted with copper bichromate. This stain of the cell 

 bodies is usually black or brownish-black, and, therefore, appar- 

 ently different in character from the blue or bluish-black stain of 

 the myelin sheath. The effect of the above treatment is to 



^Copper bichromate has been used for some years by the author as a mordant for formahn fixed 

 and preserved material when making Weigert-Pal preparations. It usually yields pictures exhibit- 

 ing all the medullated fibers with great sharpness; its only disadvantage being its tendency to make the 

 material brittle. (See Journal of Comparative Neurology, Vol. 13, No. 4. Dec, 1903.) 



