

CHTJKCH ON THE MYOLOGY OF THE ORANO UTANG. 515 



metacarpal bone of the middle finger, sending a few fibres to those of 

 the index and ring fingers. In two specimens dissected by Duvernoy, 

 he found this muscle performing the office of an Extensor proprius of 

 the middle finger only, and in another specimen it was inserted into 

 both the index and middle fingers ; see also Cuvier, 1. c. pi. 17. 



In the Gorilla, according to Duvernoy (p. 97), it goes to the index 

 only, but it is very weak. In the Chimpanzee, according to Vrolik, 

 the tendinous insertion is confined to the index, but the muscle at its 

 origin appears to be fused with the common Extensor. In an Ateles 

 I found it to terminate by two distinct tendons ; one of which was 

 inserted into the index and radial side of the middle finger, the other 

 into the ulnar side of the middle and the ring finger. In the Cebus 

 and Magot, the two tendons were inserted severally into the middle 

 and index fingers.* 



The extensor muscles in the human subject are very liable to 

 variations, and the commonest resemble those arrangements found 

 normally in the Quadrumana. Mr. Hallett says of the Extensor 

 Minimi Digiti, " it is occasionally absent, being replaced by the 

 Extensor Communis; more frequently split into two tendons, or 

 two muscles even, going to the ring and little fingers." The sending 

 off of a slip to join the tendon of Extensor Communis going to the 

 ring finger is described by Vesalius.f Theile^ mentions the same ar- 

 rangement as Mr. Hallett. Mr. Hallett also describes a case in 

 which the Extensor Indicis was divided into two distinct muscles, 

 the tendon of one of them going to unite with the index branch 

 of the common extensor, while the other went to the middle finger : 

 this was the most complete irregularity met with, but many minor 

 grades were noticed. Theile§ mentions the tendon being double, a 

 branch going to the middle finger. || 



The want of specialization of this muscle in the Orang must be 

 regarded as a lower organization than that of the Chimpanzee or 

 Gorilla, which, from their myology, I should think are able to point 

 with their finger in the same manner as man. 



The Pronator Teres, Flexor Carpi Padialis, Falmaris Longus, and 

 Flexor Carpi TJnaris presented the closest resemblance to the same 

 muscles in man. But the individuality of the several muscles was 

 less marked ; they appeared to have a common origin from the inner 

 condyle of the humerus and intermuscular septum, and owing to the 

 interlacement of their fibres, none of the muscles could be traced out 

 to their individual origins. The same remarks apply to these muscles 

 in the Magot and Cebus. 



The Flexor Sublimis Digitorwm. The portion of this muscle 



* The muscles known as Eoctensores primi intermodii pollicis, Indicis and Minimi 

 digiti, appear to be mere isolated remnants of the complete second or deep extensor 

 digitorum found under various forms in the lower Mammalia. — [Eds.] 



f Vesalii Opera, vol. i. p. 258. % Encyc. Anat. torn. hi. p. 230. 



§ Wagner, Elements of Comp. Anatomy, translated by Tulk, p. 19. 



|| And sometimes this muscle is double and its deeper division gives three ten- 

 clous, to the 2nd, 3rd and 4th fingers. See Hcnle, 1. c, p. 213. 



