MYOLOGY OF THE ORNITHORHYNOHUS. 155 



very tip of the olecranon ; it is thus longer than, but not so broad nor 

 strong as, the humeral portion, and is wholly muscular without ten- 

 dinous intersection. It joins the other portion at the common tendon 

 below. 



Between these two portions, and partly separating them, a small 

 distinct fusiform muscular belly lies embedded. It has tolerably defi- 

 nite and distinct origin from the little tubercle qn the base of the 

 humerus just internal to the ulnar facet; it runs along in the sub- 

 stance of the digital flexor for an inch or so, and then contracts into 

 a delicate thread-like tendon that we traced distinctly to the wrist, 

 and there lost without making out special insertion. We found 

 what we take for the same muscle in the opossum (D. virginianus) ; 

 there it has precisely the same disposition and relations. It cannot 

 be flexor digitorum superficialis, because we find the latter confined to 

 the palm ; nor flexor longus proprius pollicis, since this last must be 

 represented in the portion of the common flexor that corresponds to 

 the first tendon going to the thumb. We take it to be palmaris 

 longus. 



The common flexor of the fingers splits at the palm into five, not 

 four, equal and similar tendons. Morphologically speaking, we hold 

 " flexor longus proprius pollicis," when this exists independently, to 

 be merely a differentiation from the common " profound " or perforat- 

 ing set of flexing tendons. Here the deep flexor remains intact, and 

 there can be no dissentaneous motion of the thumb, even did the close 

 webs permit it. The single great tendon passes the wrist flanked on 

 either hand by the wrist extensors (radial and ulnar), filling up the 

 depression between the two prominent carpal bones, to which the 

 tendons of the muscles last named are attached. It fills the palm to a 

 level, forming a thick indissoluble tendinous band, permeated with 

 several small irregular gritty specks, like imperfect sesamoids one 

 for tendons" of little and ring fingers, one for middle and index, with 

 a thumb moiety lying a little to one side of the last. A little beyond 

 the bases of the metacarpals, the tendon divides into five, as already 

 stated. These pass each to the base of the ungual phalanx of a digit, 

 bound down in their course, not only by the ordinary digital sheaths, 

 but by a small stout transverse fibrous band opposite each node. 

 Each perforates, as usual, a tendon of the superficial flexor, and has a 

 lumbricalis, as noticed in detail below. 



Extensor digitorum communis. Arising from the outer condyle next 

 after the origin of the flexor carpi radialis ; a subfusiform, laterally 

 flattened muscle wedged between the last named and the extensor 

 minimi digiti, with only one border becoming superficial. With defi- 

 nite pointed origin from the very apex of the ectocondyle, it quickly 

 becomes tendinous ; opposite, or a little above the wrist, the tendon 



