MORPHOLOGY OF EYE MUSCLE NERVES 9 



Vom Rath's method is not specific for the neurofibrils, which 

 are nevertheless deeply stained. Cell boundaries are shown with 

 special distinctness and shrinkage is slight. The process is ad- 

 vantageous in demonstrating cell relations in the stages, when 

 nervous connections of tube and somite are effected. 



Flemming's stronger formula gives excellent fixation of sela- 

 chian embryos but does not allow the use of pyrogallic acid for 

 subsequent staining. Fixation seems quite as faithful as in Vom 

 Rath preparations, but cell boundaries are not so distinct as in 

 the latter. Iron hematoxylin gives the best stain, subsequent 

 to the use of Flemming's fluid, but it is necessary to paint the 

 sections with 0.5 per cent celloidin in order to prevent their loss 

 in staining on the slide. 



For the specific purpose of demonstrating the neurofibrils 

 Cajal's method has given uniformly satisfactory results, which 

 appear somewhat less refined than those obtained by the Biel- 

 chowsky-Paton process. The Cajal method is as follows: 



1. Fix in absolute alcohol and 1 per cent ammonia for forty-eight 

 hours. 



2. Wash for one-half to three minutes in distilled water. 



3. Pyridine for twenty-four hours. 



4. Distilled water — many changes — for twenty-four hours. 



5. Two per cent aqueous solution of silver nitrate for three days at 

 35°C. in the dark. 



6. Rinse in distilled water. 



7. Four per cent pyrogallic acid in 5 per cent formalin for one to 

 two days. 



8. Paraffin sections. 



The Simarro-Cajal silver reduction method, following fixation 

 in 70 per cent pyridin, which has given such splendid results 

 when apphed to mammal and other amniote embryos has proved 

 a complete failure in the case of Squalus embryos. 



Excellent results in the differentiation of the neurofibrils have 

 followed the use of the molybdic-acid hematoxyhn process as 

 developed by Held ('09). Tissues may be fixed by various 

 methods including Zenker's fluid and Rabl's picro-sublimate. 

 The stain is effected by a solution of molybdic acid in a 1 per 

 cent solution of hematoxylin in 70 per cent alcohol. The stain 



