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the leg muscles — for instance, the tibialis posticus, which is deprived of 

 its metatarsal insertion, and sometimes even tibialis anticus is similarly 

 circumstanced ; likewise the interossei pedis are usually attached to the 

 first phalanx of each toe, while those of the hand are attached to the 

 second and third. The second set of extensors is well developed in 

 some animals, as I have described a few pages before in connexion with 

 the muscles of the other. The fourth set of digital muscles belong, not 

 to the forearm, but to the hand, and constitute a short group of flexors or 

 extensors. The examples of this series are met with under the names 

 of extensor digitorum brevis pedis, which sends differentiated slips to 

 the hallux and three or (as in the case above) four toes. This is repre- 

 sented in the hand by extensor digitorum brevis manus, described above. 

 Of the flexors in this group we have the types very much altered, on 

 account of the variety of work which they are required to do : the 

 superficial head of the short flexor of the thumb take its place as the 

 first of these ; but as the functions of the others as flexors are more 

 efficiently executed by the other before-mentioned muscles, the use of 

 these muscles is altered, and there is even in the human subject, even 

 a correct gradation of these variations. If we take the first muscle of 

 this type we will find that the extensor brevis digitorum pedis, acting 

 at an angle with its long extensor co-operator, is inserted into its ten- 

 dons at an acute angle. Secondly, the extensor brevis manus, when 

 present, is usually inserted fleshy and not tendinous into the long exten- 

 sor tendons. Thirdly, the representative of the same muscle on the flexor 

 aspect of the foot is inserted into the tendons of the flexors, but nearer 

 to the ankle, so as to correct their obliquity, and thus the short extensor 

 of the second, third and fourth toes becomes the musculus accessorius 

 pedis. In the hand such a correction is not wanted usually ; but in 

 some animals, as Hyrax, it is found assisting and regulating the action 

 of the flexors (Messrs. Murie & Mivart, " Proceedings of the Zoological 

 Society, 1865, p. 345). This muscle arises in these animals from a 

 cartilaginous disc in the palmar fascia ; but as many animals have, as 

 in man, the flexor tendons running straight, and neither needing an 

 accessory or a corrective, the insertion of the muscle is, by a slight 

 gradation, shifted to the deeper aspect, and then to the superficial 

 aspect of the palmar fascia, and the muscle still retaining its bony origin 

 from the pisiform, appears as in the agouti; but losing this last relic of 

 bony origin., we find it in the hand of man as a few scattered superficial 

 fibres passing from the hypothenar eminence to the edge of the palmar 

 fascia under the name of palmaris brevis. 



Of the true hand muscles we find likewise there are several types : the 

 lumbricales are perhaps differentiated accessory slips of the long flexor. 

 The metacarpals have each got a pair of palmar and a pair of dorsal 

 muscles along their sides, the interossei ; the former as flexors and late- 

 ralizers, the latter as extensors and lateralizers. As the two lateral fin- 

 gers have specialized actions, these muscles are modified for them, but 

 the typical forms are the same. We can express these modifications most 

 clearly in the form of a table, thus : — 



