36 
the origin of this head extends upon the dorsal or radial aspect 
of the radial tuberosity, and there encroaches upon the outer 
aspect of the bone distal to the insertion of the infraspinatus 
muscle. From the latter it is limited by an oblique line running 
spirally round the neck of the humerus for a short distance. In 
the distal half of the brachium this head lies superficial to the 
lower part of the origin of the “inner” head of the muscle, and 
its inner margin is thinned out upon the surface of the latter, 
though not quite separate from it. About the middle of the 
brachium the musculo-spiral nerve winds forwards between the 
two layers (outer and inner heads) in order to reach the ventral 
aspect of the limb above the prominent part of the ectocondylar 
crest. 
The “inner” head (figs. 6 and 7, 72.h.¢7.) is more massive than 
the “outer.” Proximally it reaches up beyond the insertion of 
the teres major. In one specimen the tendinous layer on the 
ventral aspect of this head was found to extend upwards ventrad 
of the insertion of the teres major, while the proper fleshy fibres 
of the bend reached up dorsad of the same muscle. The ventral 
tendon was certainly of the nature of internal intermuscular 
septum, muscular fibres arising from its dorsal aspect, and I may 
hazard the conjecture that its prolongation upwards in front of 
the teres major represented the faint remnant of a coraco- 
brachialis muscle which is otherwise entirely unrepresented in 
this animal. 
Short fibres of the inner head of the triceps fill up the great 
space in the lower part of the brachium between the humerus. 
and the olecranon. These fibres are covered by the outer head, 
and the outer margin of this part of the muscle is in deep appo- 
sition with the proximal border of the anconeus externus muscle,. 
from which indeed it is not very definitely separable. The 
scapular head forms a thick but superficial lamella of the muscle, 
which is inserted along the extensive convex edge of the recurved 
olecranon. A few of its most postaxial fibres adjacent to the 
latissimus dorsi terminate along with the latter in the aponeurosis 
of the forearm. | 
The fibres of the humeral heads of the muscle form a deeper 
fleshy stratum also inserted into the olecranon beneath the 
scapular fibres. They are only continuous with the latter at 
their insertion. ; 
The question of the representation of the dorso-epitrochlearis muscle 
has already been discussed, and a summary of the morphology of this 
muscular element in mammals under the name of M. anconeus quintus 
will be found in a memoir upon the subject by Wenzel Gruber.* 
¥* lvili., page 9, et seq. 
