Lecturer on. Anatomy and Physiology in the College; Professor of Anatomy in the University of Cambridge; etc. LECTURE III.-7une 21st, X872.-(Condcuded.) THE dorsal or supinato-extensor mass in the lower limb, if we except the covering fascia, is quite cut off from the upper segment of the limb. In many of the lower animals, however, it takes an origin from the femur. In some, it is extensively connected with the femur and with the thigh-muscles, and is extensively inserted into the leg-bones,

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... as to form an important adjunct to the extensors of the leg. A similar disposition to this is retained in the upper limb, forasmuch as a considerable part of the supinato-extensor mass arises from the humerus, and some part of it is inserted into the radius. It has to be observed, that this origin is confined to the radial or pre-axial condyle, because the uprising of the olecranon cuts off the mass from the mniddle and the post-axial parts of the end of the humerus. The radial sector of the superficial stratum in the upper limb arises entirely from the upper segment of the limb ; and a portion of it-in some of the lower animals, the whole of it-is inserted into the radius, constituting the supinator radii longus. This muscle is so situated as to have a flexor action upon the elbow; and, in some instances of contraction of the joint, it presents a formidable obstacle to extension. A portion of the sector runs on at a deep level beneath the elements of the deep stratum which cross it, over the carpus to the metacarpus, constituting the extensores carpi radiales. The corresponding or tibial sector in the lower limb forms the tibialis anticus, and passes from the leg-bones entirely over the ankle to the tarsus and metatarsus, there being no subdivision of it ; so that the tibialis anticus contains the blended serial representatives of the supi. nator longus and the extensores carpi radiales, besides, as presently to be mentioned, in part at least, those of the upper two extensors of the pollex. In the inturned position of the foot, the tibialis anticus becomes associated with the flexors in maintaining and increasing that inclination. Hence it commonly is necessary to divide it, as well as the tendo Achillis and the tibialis posticus, in the operation for the cure of talipes varus. The ulnar sector-the extensor carpi ulnaris-arises partly from the humerus and partly from the ulna; the ulnar fibres, which in some ani. mals serve as an insertion, here constituting an origin. It is continued in its entire thickness to the metacarpus. The fibular sector, which is the homologue of the ulnar sector, is disposed in a rather remarkable manner. It is divided into the three peronei. Of these, one-the peroneus tertius-passes to the fibular metatarsal, and so corresponds more closely than either of the other divisions, in function as well as position, with the extensor carpi ulnaris. A second part of the sector, forming the peroneus brevis, passes to the same metatarsal; but, in consequence of its travelling behind the malleolus, instead of in front, it becomes, although supplied by a branch of the same nerve, an antagonist to the former portion and a flexor of the ankle. In this it resembles the extensor carpi ulnaris of