146 
PROFESSOR A. MACALISTER ON THE 
Professor Humphry also found some fibres passing into the triceps from the posterior 
surface of the tendon of the coraco-brachialis (Joe. cit. p. 305) ; this likewise I have not 
found, except in the three species of Pteropus. In Eleutherura the triceps has two 
scapular heads, of which the external is three times larger than the internal. The long 
head is partly double at its origin in Pteropus edulis. 
As already mentioned, the only traces of the dorsi epitrochlearis exist in the Yesper- 
tilionidee ; in all of these it is extremely weak, but it is largest proportionally in the 
Pipistrelle. 
The humeral head of the triceps is single in Megaderma and is external ; indeed Pro- 
fessor Aeby regards it in all Bats as single and with germs of two lateral heads (Siebold 
& Kolliker’s Zeitschrift, x. p. 41). In Bhinolophus diadema there is a single long 
external humeral head and a double scapular origin, and no fibres for the lower part of 
the back of the humerus. In Cephalotes there is a large external humeral origin ascend- 
ing to the head of the humerus, and a small internal slip separated by the musculo-spiral 
nerve. In Vampyrops the two parts are separate, but soon coalesce. In Plecotus the 
humeral triceps is excessively weak and single ; it is the same in the Pipistrelle, a little 
stronger in Vespertilio murinus and the Noctule ; in all the fibres pass down the humerus, 
and are inserted into the extremity of the ulna. In all the species a detached sesamoid 
bone exists in the tendon above the extremity of the ulna, exactly resembling a patella ; 
this has been long known, having been described by Gratiolet and Ge.offroy St. Hilaire 
(“ Sur 1’existence d’un osteide dans le tendon de Fextenseur de Favant-bras,” Nouvelle 
Bulletin Scient. Philomath, p. 158, 1826). 
The musculo-spiral nerve winds round the humerus at its lower fourth, lower in Me- 
gaderma than in any other species ; the ulnar nerve passes along the brachial artery, then 
passes behind the inner condyle, sending a filament to the little finger, one to the dactylo- 
patagium latus, and two to the back of the forearm ; this arrangement was easily trace- 
able in Boctulina. 
The proportion between the flexors and extensors has been studied by Professor Aeby 
of Basel; he finds the triceps to be 25’65 per cent., the biceps and brachialis 32T3 (in 
Table xvi. p. 86 he has misplaced these numbers ; but this is as they should be from his 
data, p. 85). 
The muscles of the forearm are singularly beautiful and well deserve a careful study ; 
the flexors are inferior in strength to the extensors in the forearm ; but this is exactly 
made up by the preponderance of short flexors in the manus, which render these groups 
of muscle nearly equal ; the motions which they produce are simple flexion and extension 
in a single plane : rotation of any kind is not permissible in the elbow- or wrist-joints ; as 
the latter is only a single forearm bone, its possibilities of motions are thereby simplified. 
The usual four groups of muscles, supinator, pronator, flexor, extensor, are represented 
in general as follows : — 
Pronator radii teres (Plate XIV. figs. 1, 5, & 5, d) is said by Cuvier to be absent, as 
well as the pronator quadratus and the supinators (Leyons, i. p. 298). Meckel admits 
