Mackintosh — Muscular A natomy of CJwlcepns didactylus, 73 



only found the condylar origin, and the insertions of both tendons was 

 into the proximal parts of the metacarpals. 



Extensor digitorum longus presented no feature of interest, extend- 

 ing from the outer condyle and from the ridge on the back of the 

 radius to the terminal phalanges of the digits. The radial oi'igin is not 

 mentioned by Professor Humphrj-, 



Extensor minimi digiti (auricularis) arises from the intermuscular 

 septum on the back of the forearm^ being traceable as far as the upper 

 third ; the tendon runs through a separate sheath in the annular liga- 

 ment, expands on the ulnar side of the third digit, and joins the ten- 

 don of the long flexor. This muscle is not described by Professor 

 Humphry. 



Extensor carpi ulnaris arose in both specimens from the external 

 condyle, olecranon and ulna, and divided into two parts, one of -which 

 becomes tendinous and is inserted into the proximal dorsal aspect 

 of the first phalanx of the third digit; the second segment, which is in 

 fact ah ulnaris quinti, ends in a tendon which joins that of the extensor 

 of the little finger at its insertion. In Professor Humphry's specimen 

 the muscle ended in two tendons running to the third and fourth 

 digits. 



Extensor ossis metacarpi pollicis (extensor poUicis primns) arose 

 in both from the greater part of the posterior surface of the ulna, and 

 was inserted into the trapezium. 



Extensor secundi internodii pollicis was absent. 

 Extensor indicis was normal, running in both animals from the 

 middle of the ulna to the rudimentary second digit. 



Interossei are arranged somewhat similarly in both. In our spe- 

 cimen the first and second act as abductor and adductor annularis, re- 

 spectively ; the third placed between the third and fourth metacarpals 

 runs to medius ; the fourth and fifth between the second and third me- 

 tacarpals go to medius and index, respectively ; the sixth, which is 

 bicipital and placed between the first and second metacarpals, goes to 

 index, whilst an additional one, which does not seem to have existed 

 in Professor Humphry's specimen, extended from the pisiform bone 

 to the ulnar side of the second metacarpal.* 



Lumbricalis single, arising between the tendons of flexor di- 

 gitorum, divides into two parts, one going to the radial and one 

 to the ulnar side of each, digit, the latter attachment apparently not 

 existing in Professor Humphry's specimen. 



We found a tendinous band passing from the tip of the rudimen- 

 tary fifth digit to the first phalanx of the fourth. 



* Professor Humphry arranges them thus : — One hetween Met. I. & II. to the 

 radial side of the extensor tendon of digit II. ; one between Met. IV. & III. to 

 ulnar side of extensor tendon of digit III. ; one between Met. II. & III. on palmar 

 aspect passing to ulnar side of extensor tendon of digit II. ; and one on the dorsal 

 aspect to the radial side of the extensor tendon of digit III. There is also an ad- 

 ductor of digit II. from pisiform to ulnar side of first phalanx (which seems to 

 represent the "additional" muscle mentioned above). There is also a second set 

 of "phalangeal" interossei, two in number, from the apposed sides of the two 

 second phalanges to the apposed sides of the two extensor tendons. 



E. I. A. PKOC, SEE. II. VOL. IT., SCIENCK. L 



