MYOLOGY OF THE CHEIEOPTERA. 
135 
This muscle is proportionally largest in the Vampyres, especially in Artibeus ; is short 
and thick in Plecotus and the Pipistrelle. It has in general, properly speaking, no 
clavicular origin, as Professor Humphry states; but that author does not notice the 
origin from the sterno-clavicular ligament and the somewhat kidney-shaped epicoracoid. 
This enormous muscle is by far the largest in the body of the Bat. In Megadermci a 
few fibres are attached to the sternal end of the clavicle, and the entire muscle is 
much thinner than in the Vampyres. The degree of separation existing between this 
muscle and the clavicular deltoid is very variable ; they are perfectly distinct in the 
species of Bhinolophus, especially 11. diadema ; in Eleutherura they are conjoined ; nearly 
so in the Pteropus Edivardsii ; quite separate in Pteropus edulis and in Megaderma. In 
the Vespertilionidae, as remarked by Meckel, they are combined. In my specimen of 
Pteropus edulis, which was 36 inches in expanse of wing, this muscle weighed an ounce 
and one tenth. 
The second part of the great pectoral, or the pars clavicularis, is variable in size and 
separateness, completely covered by the sternal part and small in Cephalotes ; it arises 
from the anterior sterno-clavicular ligament and the inner half of the under border of 
the clavicle ; it is inserted above the sternal pectoral into the pectoral crest ; it lies on the 
costo-coracoid membrane and the coracoid process. In Vampyrops it is, at its commence- 
ment, completely under cover of the sternal part, but at its insertion it is the more super- 
ficial of the two. In Macroglossus and Pteropus this portion, though in its course and 
termination on a plane posterior to the sternal part, is less covered at its origin, and 
passes over the coracoid process. In these it arises from nearly the whole length of the 
clavicle (two thirds in Pteropus medius , one third in Edwardsii, Humphry, even less in 
Pteropus edulis) ; its lower surface is fiat and fleshy where it lies on the coracoid, from 
which it is separated by loose areolar tissue ; but no bursa intervenes, and the relation of 
the parts in nowise partakes of the nature of a pulley. This portion in the Plecotus 
overlaps the sternal part for one half, and the same is the case in Vespertilio. In Mega- 
derma it is more distinctly separate than in any other species, the anterior cutaneous 
nerve intervening between it and the pars sternalis ; in this species it has much the 
appearance of the human anomaly pectoralis minimus described by Professor Wenzel 
Gruber, of St. Petersburg ; it arises from the clavicle, sterno-clavicular ligament, and 
from the cartilage of the first rib ; the insertion is by a special round tendon into the 
pectoral crest of the humerus. 
The nature of this second part of the great pectoral has been a subject of difference 
of opinion. Cuvier, in the ‘ Lemons Orales,’ describes the great pectoral as tripartite, 
and regards this as its second part. Meckel describes the great pectoral as consisting 
of a superficial and two deep portions ; the first of these, he says, arises from the 
sternum and clavicle (my dissections, as noticed above, do not bear out the latter part of 
the statement ; but as he did not separate the clavicular deltoid from the sternal pectoral, 
he looked on the origin of the latter as part of that of the former), the second part is 
clavicular, and the third also from the clavicle. In their Plates of Pteropus, Cuvier 
