Hardesty, spinal Nerves of the Frog. 329 



into a vial containing i % osmic acid and set aside from 12 to 

 24 hours. 



This method has produced Tvery good results for the 6th. 

 spinal nerve at least, and does away with the exposure of the 

 eyes and nose to the tumes of the osmic acid necessary in the 

 method described in the former paper. 



The fixing and staining in the osmic acid completed, the 

 specimen was washed in distilled water from 2 to 8 hours. Dur- 

 ing this period it was brought in a Minot watch-glass under the 

 dissecting microscope, and most of the periganglionic capsule 

 and other adherent tissue carefully dissected away and the peri- 

 pheral part of the nerve trunk clipped off close to the ramus 

 communicans. Then a camera drawing was made of the nerve 

 under a magnification of eight diameters. This drawing was 

 useful later on. It could be used to show the number and 

 direction of the dorsal branches, the general shape of the nerve, 

 and the position of the ramus. In case of the small nerves 

 after they had been embedded, the drawings were especially 

 helpful in the orientation of the nerve. Also the lengths or 

 distances between the localities from which the sections were 

 taken, could be more easily ascertained from the drawings. 

 After all the free acid had been removed by washing, the speci- 

 men was passed through the increasing grades of alcohol, 

 cleared in xylol and embedded in paraffin. The embedding 

 was done in small paper boxes on the sides of which were 

 marked the date, the weight and sex of the animal, and the 

 number of the nerve. 



Thus the embedded specimen could at any time be identified 

 with the drawing which was marked in the same manner. 



Transverse sections, 4 micra in thickness, were taken from 

 the required localities and mounted, straightened out and fixed 

 to the slide by the albumen water method described in the pre- 

 vious paper. A separate slide was used for each locality. After 

 the balsam had hardened sufificiently, the section best suited for 

 counting was selected and surrounded by a ring of India ink 

 on the cover glass. 



