156 couEs, 



grows broad, thin and flat, and expands still more upon the back of 

 the hand. Individual tendons may of course be traced to the tips of 

 the digits ; but they are so blended in one common fascial expansion 

 upon the back of the hand, and upon the digits are so intimately con- 

 nected with the fibrous sheaths, that they require to be forcibly and 

 somewhat arbitrarily cut apart. Extension of the digits is absolutely 

 consentaneous, so far as this muscle is concerned. 



In the muscle is formed a small, distinct, muscular belly, with a 

 delicate abortive tendon, not traceable to definite insertion. This 

 unquestionably represents one of the deep (special) extensors — either 

 extensor indici or of a pollical internode; more probably the former. 



Extensor minimi digiti. — Lying next to the preceding, as large as 

 it, and perfectly distinct; in greatest part superficial, overlying the 

 last described, and itself partly overlaid by the flexor carpi ulnaris, 

 a short, stout, spindle-shaped muscle arising from the ectocoudylar tip, 

 and passing to the tip of the little finger. Its tendon is very distinct 

 to the back of the hand, where it partakes of the general fascial ex- 

 pansiveness, and is scarcely distinguishable except by arbitrary dis- 

 section. 



The constancy of this muscle is as remarkable as that of the exten- 

 sor longus proprius pollicis of the foot, and is specially interesting 

 in such a case as the present, when proper thumb, muscles abort or 

 disappear. It goes far towards substantiating the antitypy that we 

 hold exists between the little finger and great toe. 



Extensor ossis metacarpi pollicis. ^^ Abductor pollicis longus." — While 

 the foregoing extensors are superficial, this, like the supinator brevis, 

 is deep-seated, being entirely overlaid above. It is the only special 

 thumb muscle — others goiug to the internodes being wanting. It 

 lies upon the back of both bones of the forearm, arising fleshy from 

 both, but mostly from the ulnar shaft, its middle third, as high up as 

 the elbow joint and insertion of aucongeus; its radial origin is only 

 from the head and a trifle of the shaft of that bone. The muscle be- 

 comes tendinous a little below the middle of the forearm, where its 

 obliquity increases to enable it to gain the radial side of the limb ; it 

 passes under the tendon of the flexor carpi radialis, and over that qf 

 supinator longus, across the foot of the radius, and thence I'uns to 

 the base of the first metacarpal, where it is more definitely inserted 

 than the other extensor tendons are. From its insertion and the ob- 

 liquity of its tendon, it is a pure abductor, or web-spreader, rather 

 than an extensor. 



Although this muscle is inserted into the base of a metacarpal, in- 

 stead of into a digital internode, it is essentially one of the digital ex- 

 tensor set ; and as explained at greater length below, we refer to the 

 " peroneus tertius " of anthropotomy (a muscle that, in some animals, 



