Dunn, Medullated Nerve Fibers. 687 



The ventral roots of the Vlllth, IXth, and Xth spinal nerves, 

 Gaupp's enumeration, were identified, torn loose from the cord, and 

 left free in the spinal canal. Every precaution was taken to pre- 

 vent the injury of the dorsal roots, the spinal ganglia, or the nerves 

 distal to the ganglia, and later microscopical observation showed 

 the intact condition of these tissues and the anticipated degenera- 

 tion in the ventral roots. 



After the readjustment of the tissue flap, the skin wound was 

 sealed with collodion. Healing was by primary intention, and while 

 slow, seemed to be complete before the shedding of the collodion 

 dressing. 



For the eight months following the operation the frog was kept 

 in a metal refrigerator at a temperature below that of the room but 

 above the freezing point. While the temperature was not absolutely 

 uniform, owing to some irregularities in replenishing the ice, the 

 conditions approximated those furnished by the ordinary laboratory 

 method of keeping frogs in a tank with access to running water. As 

 usual with laboratory frogs, attempts at feeding were unsuccessful. 



The physical sigTis of the success of the operation were the flac- 

 cidity of the leg under various conditions, and the absolute failure 

 of motor response by the operated leg to unpleasant stimuli, even 

 when the stimuli were so intense as to produce vigorous motion of 

 the remainder of the body. Xo marked changes were noted either 

 in the skin of the leg or in the size of the muscle mass, and later 

 microscopic examination of the leg muscles on the two sides showed 

 no loss of striation on either side, but a slightly less deep stain for 

 the operated leg. 



The nerve tissue to be examined was partially fixed in situ with 

 a 1 per cent solution of osmic acid, and after removal was immersed 

 in such a solution for twenty-four hours. The material was then 

 washed thoroughly in distilled water, dehydrated, cleared and im- 

 bedded in paraffin. The sections were cut transversely to the long 

 axis to a thickness of four micra, and mounted in the usual way. 



The measurements of individual nerve fibers were made by the 

 aid of the ocular micrometer. 



The methods of enumeration were those elaborated by Hardesty, 



