The Motor Ganglion Cells of the Frog's Sjnnal Cord. 55 



0.204 sq. mm., with 2/239 fibres, while the seventh, eighth, 

 ninth nerves which supply the lumbar plexus, have an area 

 of 0.359 sq. mm., with only 1,453 fibres, that is, with approx- 

 imately the same area, there are only two thirds as many 

 fibres. The fourth, fifth and sixth nerves stand in size of fi- 

 bres between the two groups, while the tenth nerve has 

 the smallest fibres, possibly since it contains those which 

 supply the lymph hearts. 



Since the muscle fibres of the hind legs are so much larger 

 than those of the fore legs one cannot help thinking that there 

 is a relation between size of motor fibres and the muscle fibres 

 supplied by them. But this question needs further investi- 

 gation. 



Another striking fact, like that of the size, and found also in 

 the ganglion cells, is that of the number of fibres in brach- 

 ial and lumbar plexus respectively. In spite of the smaller 

 size of the anterior extremities they receive an equal or 

 greater number of nerve fibres than do the hind limbs. 

 These facts will become more apparent by the following table : 



TABLE V — MOTOR FIBRES. 



