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Show 692 ON THE ANATOMY OF ATHERURA AFRICANA. [Nov. 20, plantar surface. I was unable to satisfy- myself as to the nerve-supply of the lumbricales. The pudic nerve comes almost entirely from the 2nd S. and supplies the muscles and skin of the perineum. In comparing the plexuses of Atherura with those of Erethizon as figured by Mivart', it will be noticed that the brachial plexus of the latter receives no branch from the 5th C. as it does in Atherura and M a n , but that all the branches of the plexus are as easily traced to their origins from the spinal cord as they are in Atherura. In the sacral plexus the small sciatic of Erethizon seems to rise from the same place as the pudic of Atherura, viz. the 1st aud 2nd sacral, but then no indication is given in the figure of the origin of the pudic in Erethizon. The nerves of a specimen of Hystrix cristata, which I dissected in order to compare with those of Atherura, show a striking resemblance to the latter animal. The following are the only differences I noticed :-The circumflex comes from the 6th and 7th C. instead of the 5th and 6th. The external cutaneous communicates with a branch of the median going to the brachialis anticus and sends no cutaneous branch to the forearm. The median rises from 5th, 6th, 7th, and 8th C. and 1st D., and receives a large branch from the external cutaneous, Avhich branch is bou*nd up with the median, and eventually comes off to supply the outer side of the forearm. The nerves to the teres major and latissimus dorsi which I failed to notice in Atherura rise in Hystrix from the circumflex. The supplies of the fingers and toes are identical in both animals. The arrangement of the nerves in the hand and foot already mentioned seems of some interest from the point of vieAv of variation. In M a n the ulnar supplies one finger and a half on the palmar surface, and the external plantar one toe and a half on the plantar surface. In Atherura and Hystrix neither of these nerves supplies any of the fingers or toes. I do not think that this arrangement is peculiar to the Hystricidce, because it occurs also in the Hamster and possibly in other Bodents. Since M a n and the Porcupines agree in having the same arrangement of nerves in the hand as in the foot, but differ in that arrangement, it looks as if the cause that brought about the change of arrangement Avas identical for the two extremities. 1 P.Z.S. 1882, p. 279. |