Variations va Spinal Nerves of Hyla aurea. 269 



to the Semimembranosus, to both heads of the Semitendinosus, 

 and to its posterior portion, to the inner surface and body of the 

 Adductor magnus, to the Biceps, and to the Rectus internus major. 

 Beneath the Biceps the sciatic divides, forming the Tibialis and 

 Peroneus. The former passes down the leg to the foot, giving off 

 nerves supplying the skin, the Gastrocnemius, the Tibialis posticus, 

 the flexors of the fingers, the Abductor hallucis, and lower down 

 divides into two nerves, the one supplying the ventral surface of 

 the digits, and the other the deep or under-surface of the muscles 

 of the sole. The second division of the sciatic, the peroneal, 

 gives off immediately after its origin, nerves to the skin. It then 

 divides into two — one half lies between the surrounding muscles 

 and gives off branches to the Tibialis anticus, Peroneus, and 

 Flexores tarsi anterior -And posterior. The other half runs straight 

 through the substance of the Extensor cruris brevis, to which it 

 gives off a small branch, and continues clown to the ankle, where 

 it joins the other half, close to the bone, and below the Flexor 

 tarsi posterior. Just before it unites, however, a branch is given 

 off running to the skin and extensors of digits IV. and V., 

 while the large nerve, formed by the junction, runs down to 

 supply the extensors of digits I., II. and III., and the skin of the 

 toes. This peculiar branching and junction of the peroneal nerve 

 would appear to be the same as that described by Ecker fur 

 Pa/ia* — where the Peroneus medialis joins the Peroneus lateralis, 

 forming a common stem, the peroneus communis inferior. 



The Xlth. nerve is a thin nerve, and may have a direct or an 

 indirect connection with the sacral plexus. In the former case, 

 in which XL always take some part in the formation of the 

 sciatic nerve, the whole nerve may enter X., or it may join X. 

 by two or more of its own branches, either passing entirely into 



X. in this way, or sending down a branch which has an indirect 

 communication with X. This latter means of connection is by 

 far the most frequent, and is seen in instances where branches of 



XI. join branches of X. or of the sciatic, often forming a net- 

 work. 



Nerve XII., which Aclolphi mentions as occurring in one per 

 cent, cases in Bufo variabilis, and very rarely in Pelobates fuscus, 



* Efker : loc. cit. , p. 196. 



