20 Journal of Comparative Neurology and Psychology: 



but at the same time it is often larger than the Vth and in some re- 

 spects resembles the Vllth which belongs almost entirely to the lum- 

 bar distribution. Morever, the Vlth was employed in a previous in- 

 vestigation ('oo) and is included in this in order to accumulate data con- 

 cerning it. The IXth nerve was chosen because it is one of the largest 

 spinal nerves in the frog, and differs from the Vth and Vlth in that all 

 the fibers of its trunk are contributed to the lumbar plexus. These three 

 nerves alone are considered, it being assumed that whatever conditions 

 found true for these are approximately true for the remaining spinal 

 nerves. To enumerate the ganghon cells and the nerve fibers in the 

 dorsal and ventral roots and the trunks of the entire ten spinal nerves 

 would have been so arduous a task that the additional information 

 probably to be obtained by such was considered a reward scarcely 

 sufficient for the ordeal. 



To obtain a series ranging as gradually and as widely as possible, 

 each specimen was chosen with reference to its body weight. The 

 smallest specimen of Rana virescens obtained for this observation had a 

 body weight of 10.4 grams. Smaller specimens may be obtained at 

 certain seasons of the year just after the transition from the tadpole 

 stage. The lai-gest specimen of the series weighed 63.4 grams and 

 was, of course, female, since the males seldom exceed 50 grams whi^e 

 the females have been known to attain a body weight of 80 grams 

 \witji the ovaries removed. 



In each case the anin^al was chloroformed in the usual way and, 

 if female, the ovaries were removed. It was then weighed and its 

 body weight and sex recorded. The procedure in dissecting, fixing, 

 imbedding, sectioning, etc., was much the same as that followed in the 

 previous investigation and it is there given in detail. The spinal cord 

 was laid bare from the ventral side, the spinal ganglia and dorsal 

 branches carefully exposed and dissected free with the aid of the dis- 

 secting microscope. Avoiding pulling and stretching, the dorsal and 

 ventral roots were clipped with fine scissors close up to the spinal cord 

 and the nerve trunk near its junction with the ramus communicans. 

 Then the ganglion with the roots and portion of the nerve trunk at- 

 tached was laid on a small piece of card-board. There the roots were 

 arranged straight and parallel with each other, and the dorsal branches 

 straightened out parallel with the nerve trunk in order to obtain trans- 

 verse sections of the two with the same stroke of the knife. In doing 

 this, careful use of the dissecting lens was always advisable lest some 

 of the smaller of the dorsal branches should be overlooked and should 

 remain tangled or doubled back upon themselves, and thus in the sec- 



