400 Harris Hawthorne Wilder, 



carpale IL near the base of tlie bone, and thus acts as an abductor 

 of the digit, completing the System formed by the tendons of In- 

 sertion of the humero-metacarpalis and its accessory slip. 



M. extensor ulnar is (eu). This muscle occupies the outer 

 (ulnar) margin of the leg and is partly overlapped by the humero- 

 metacarpalis. It arises frorn the lateral condyle of the humerus, 

 along the margin adjacent to the olecranon process of the ulna, and 

 runs down over the dorsal surface of this latter bone, covering it 

 completely. The more superficial and marginal fibers are the longest, 

 and enwrap and conceal the others in such a way that the muscle 

 needs to be drawn away from the limb a little and unrolled, as it 

 were, in order to appreciate its method of insertion; this has been 

 done in the figure (Fig. 22) and shows the termination of the area 

 of insertion along an oblique Line on the lower part of the ulna 

 and on the margin of the ulnare-intermedium. Above this line the 

 remaining fibers insert, covered by the more superficial ones, so that 

 the total area of insertion includes the entire length of the shaft 

 of the ulna along its marginal border, extending, at about the 

 middle of the shaft nearly or quite across the bone. Aside from 

 this extensive insertion on the ulna a few of the outer fibers become 

 inserted into the marginal aspect of the ulnare-intermedium, beyond 

 which the fascia continues over the edge of the paw and invests 

 the short finger muscles lipon the flexor side. 



Mm. extensores breves (eb2—5). These small muscles are 

 four in number, one for each digit, and appear superficially as oval 

 beilies, interdigitating with the slips of the humerometacarpalis. 

 They arise from the distal margins of the carpalia that correspond 

 to the digits to which they belong, carpale 4 + 5 giving rise to 

 two, as would be expected. The bellies are continued into long, 

 narrow tendons, but partially differentiated from the aponeurosis 

 that Covers the dorsal surface of the digits, and appear as thickened 

 stripes along the middle of the fingers. These nascent tendons 

 insert into the bases of the terminal phalanges. 



As stated in detail under M. humerometacarpalis, these short extensor 

 tendons appear in higher urodeles as the proper tendons of this latter 

 muscle, Converting it into an extensor digitorum communis (s. sublimis). 

 The steps of this change are very gradual and are well seen within the 

 limits of the Order, the changes being due to modifications in the 

 relationships of the two muscles in question. Thus in Cri/ptobranchus, in 

 which these tendons are ascribed to the humerometacarpalis (forming an 

 •extensor digitorum longus) the lateral tendons to the bases of the meta- 



