William Selby Church

“ 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. ”

“ In Man, it is by no means unfrequent to find the sternal portion divided into two or more parts; the arrangement met with in the Magot is described in the human subject by Theile; [8] and Mr. Hallett [9] mentions a very similar one as occurring in man.
The Pectoralis Minor presented the same appearance as in man; in the Gorilla, Duvernoy states that it is divided into two portions ”

“ In the Cebus and Magot, the two tendons were inserted severally into the middle and index fingers. [11]
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. ”

“ 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, l.c. pl. 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. ”