Variations in Spinal Nerves of Hyla awrea. 267 



Nerve IV. passes outwards from its foramen between vertebra? 



III. and IV., and runs near, and almost parallel to III., with 

 which, as before mentioned, it has a communicating branch, or 

 with which it may sometimes fuse for a longer or shorter distance. 



IV. is a thin nerve, never even approximating III. in size, as 

 contrasted with Bufo variabilis in which IV. is stated by 

 Adolphi* to be sometimes the thickest in the body. It gives off 

 branches to the Transversa-scapularis major, very rarely one to 

 the coraco-clavicular, and always, a branch which runs through 

 the Obliquus abdominis internum to the Rectus abdominis muscle 

 where it branches, and finally ends in the skin, being known as 

 the Thoracicus inferior nerve. 



Nerves V. to VII. are thin. They pass out obliquely back- 

 wards and outwards, and then downwards, on the ventral surface 

 of the Intertransversarius muscle, and piercing the Obliquus 

 interims divide forming the Ramus muscularis, and Ramus 

 cutaneus abdominalis, supplying therefore the muscles and skin 

 of the body wall. I have seen no trace of communication 

 between V. and the brachial plexus, such as Adolphi has 

 observed in Pelobates juscus. f But in one case, there was on 

 both sides of the body a well-defined branch passing from VII. 

 to join VIII. above the origin of the ileo-hypogastric nerve. 



Nerves VIII. to XI. form the sacral plexus. They pass out 

 from the vertebral column and run backwards parallel with the 

 urostyle into the pelvis, giving rise to the ileo-hypogastric, crural, 

 and sciatic nerves, besides branches to the alimentary canal, 

 oviduct and bladder. Nerve VIII. is generally somewhat thin, 

 and in the great majority of cases forms the Ileo-hypogastricus 

 nerve without any assistance from IX., though in a few 

 instances fibres of IX. enter VIII. above the origin of the 

 ileo-hpyogastric, and in one case, two ileo-hypogastrics were 

 present, one composed of VIII. fibres only, the other of IX. 

 fibres only, both having the same destination. In each case 

 where IX. enters into the composition of the ileo-hypogastric, 

 VIII. is somewhat thinner than usual, but VIII. is also thinner 

 when IX. has no connection whatever with the ileo-hypogastric. 

 This nerve divides as in Rana into two branches, the Ramus 



* Morph. Jahr. xxii., 1895, p. 451. t Loc. cit. xxii., 1895, p. 451. 



