102 Journal of Comparative Neurology. 



with small scissors or fine bone forceps incisions were made 

 in the dorsal muscles just under the position of each spinal 

 ganglion in order to allow the reagent to reach the dorsal branch- 

 es more freely. 



The head was next severed well above the origin of 

 the first spinal nerve and, with a fine pipette, i % osmic acid 

 was forced under the cord washing out the cerebro-spinal fluid 

 and replacing it with osmic acid. The cord was left in position 

 at this stage lest its removal should disturb the normal tension 

 of the nerve roots or otherwise injure them. The whole was 

 then placed for lo or 15 minutes in a vial containing a one-fifth 

 one per cent, solution of osmic acid and this was frequently 

 agitated. The idea in using the weaker solution was to insure 

 a slower fixation of the connective tissue investments. It was 

 thought that a slower fixation would result in a less violent con- 

 traction and consequent condensation of the nerve bundles and 

 thus also allow a more rapid penetration of the stronger solu- 

 tion which follows. 



At the end of the i 5 minutes the specimen together with 

 the weaker osmic solution was transferred to a dish under a dis- 

 secting microscope. With the eyes and nose of the observer 

 protected from the fumes of the acid, each nerve root was gen- 

 tly severed from its connection with the spinal cord and the 

 cord removed. Next each nerve trunk was severed a few milli- 

 meters distal to its connection with the ramus communicans and 

 the ramus itself cut. Then with the aid of a fine tentaculum 

 and small spring scissors (under an enlargement of 16 diameters) 

 each nerve was detached and removed from the intervertebral 

 foramen, especial care being taken not to injure nor lose any of 

 the dorsal branches. The periganglionic capsule was now 

 opened and partially teased away and the nerve transferred to a 

 I % solution of osmic acid. 



At the end of from 12 to 24 hours the nerves were re- 

 moved from the osmic acid solution to distilled water. Again 

 under a dissecting lens, the teasing away of the periganglionic 

 capsule and other loosely attached connective tissue was care- 

 fully completed and camera outlines were made of the dissected 



