340 MESSRS. MURIE AND MIVART ON THE (Apr. 11, 
its homologue in the Pig and Horse; but the Guinea-pig presents 
us also with the same structure. 
The coraco-brachialis comes from the rudimentary coracoid pro- 
cess, and is inserted into the humerus from the lesser tuberosity 
down to quite the middle of the shaft, in a line along the inner mar- 
gin of the bicipital groove. It lies in front of the teres major. 
We found the triceps to be divided into four distinct portions, 
without counting the small muscle which we have called the dorso- 
epitrochlear. The first of these, or scapular head, is very strong, 
and arises from the neck of the scapula, adherent to the teres minor 
and infra-spinatus. It has an insertion into the olecranon (fig. 5, T. 1). 
The second, which corresponds to the outer head, is nearly equal 
in size to the former. It arises from the neck of the humerus, below 
the teres minor, just behind the greater tuberosity. It is also inserted 
into the olecranon and outer condyle of the humerus (fig. 5, 7’. 2). 
The third or inner head is much smaller than either the first or 
the second. It arises from the inner side of the neck of the hu- 
merus, below the brachialis anticus, and below the insertion of the 
teres major, intervening between these two muscles at its origin. 
The insertion of this third portion is into the inner side of olecranon. 
The fourth part of the ¢riceps is much smaller and also shorter 
than the three preceding; it arises in common with the last, but is 
clearly separated from it below. It covers the posterior surface of 
the shaft of the humerus, and is inserted into the inner condyle and 
olecranon process (fig. 5, 7’. 4). 
Meckel does not appear to have observed our fourth belly of the 
triceps proper. What he calls “the fourth” is our dorso-epi- 
trochlear. 
The dorso-epitrochlear is a long and very narrow muscle. The 
origin is very different from that of the muscle usually described 
under this name. We found it to arise from the lower border of 
the infra-spinatus, and to be inserted into the olecranon by a strong 
tendinous fascia (figs. 4 & 5, D.e.). 
The supinator longus is exceedingly diminutive, and arises from 
the outer side of the shaft of the humerus, just above the common 
origin of the next two muscles, and is inserted into the radius near 
its neck (fig. 5, S./.). 
The presence of the swpinator longus is interesting, iaasmuch as it 
is wanting in the Pig and Horse, as also, according to Meckel, in the 
Hare, Porcupine, Agouti, Beaver, Rat, &c.* 
The extensor carpi longior and brevior were not quite separated 
as described by Meckelt, but the two had a common origin from 
the external condyle of the humerus, a little above the carpus giving 
rise to two distinct tendons. They have an insertion, the one into 
the metacarpal bones of the index, and the other into metacarpal 
bones of the middle digits. 
The extensor communis digitorum arises between the last-men- 
tioned muscle, and divides into two fleshy bundles which give origin 
to four flat tendons, one being inserted into each of the four digits. 
* Loe. cit. p. 304. T Loe. cit. p. 208. 
