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Show 280 PROF. ST.-GEORGE MIVART ON THE [Feb. 21, The female sexual organs have been described by Hunter ; see his ' Essays and Observations,' vol. ii. p. 223. The brain presents a much less decidedly quadrate form than that of the Porcupine (most probably Hystrix cristata)'figured by Leuretl; and it is even more smooth, there being but a single short and slight depression (or rudimentary sulcus) at the hinder end of the most anterior third of the dorsum of each cerebral hemisphere. The pituitary body is very large, and the corpora trapezoidea well developed. The brachial plexus2 is formed by the sixth, seventh, and eighth cervical nerves together with the first dorsal. The main part of the eighth cervical, having received a branch from the seventh cervical and another from the first dorsal, is continued as the median nerve, a smaller branch from the same junction constituting the ulnar nerve. The musculo-spiral nerve is formed by the smaller branch of the eighth cervical uniting with a portion of the seventh cervical. The circumflex nerve arises by two roots-one a branch of the sixth, and the other of the seventh, cervical nerves. The external cutaneous nerve is formed mainly by a branch of the sixth cervical ; but it receives a small filament from the root of the circumflex nerve just after the latter has been formed, as above stated. The internal cutaneous springs from a branch of the first dorsal, which receives a branch from the seventh cervical root of the median nerve. The lumbo-sacral plexus is composed of the last four lumbar and the first two sacral nerves. It is very simple, with little interlacement. The anterior crural nerve is formed by the first two of the six, from the junction of which the obturator nerve is also given off. The great sciatic nerve is formed by the last two lumbar nerves only; while the small sciatic nerve springs from the junction of the two sacral nerves. LlMB-MuSCLES OF ERETHIZON. Muscles of the Fore Limb. Panniculus carnosus.-The dorsal portion of this muscle is inserted into the pectoral limbs partly over the spine of the scapula by attachment to the fascia investing the supraspinatus, and partly into the outer surface of the humerus (between the deltoid and the outer part of the triceps) down to the apex of its deltoid crest. The abdominal portion of the same muscle is inserted into the humerus outside the greater tuberosity and inside the upper part of the deltoid crest. The pectoralis is so united with the ventral part of the panniculus that they seem like two parts of one muscle. The true pectoralis however, arises from the sternum, and is inserted into the distal 1 See plate iii. of Leuret and Gratiolet's ' Anat. Comp. du Systeme Nerveux ' The brachial and lumbo-sacral plexuses were dissected out for m e bv M r W . Pearson; and the drawings aa-e from his dissections. |