1895. ] NEW YORK ACADEMY OF SCIENCES. 235 
ten and puberty, it will be found in every instance connected 
with the so-called sub-coracoid centre of ossification. 
Hence our division of the muscle into glenoid or scapular, and 
coracoid heads, while convenient as corresponding to adult con- 
ditions, should not cause the fact to be forgotten that the 
Biceps is entirely a coracoid muscle in in its origin. Wemight, 
considering the probable significance of our coracoid ossification, 
speak of the coracoid or long and precoracoid or short head of 
the muscle. The origin of the Biceps taking place in this man- 
ner from a single skeletal element, it is not surprising to find 
the consolidation of the two heads, which are present in man 
and the primates generally, to be of very frequent occurrence in 
lower forms. It will then depend upon the prominence of the 
coracoid element, and the relation of the origin to the glenoid 
socket, whether this single head will be denominated as the 
coracoid or glenoid muscle. 
B. Insertion. 
In like manner we find a considerable range in variation in the 
insertion of the muscle. It may be attached to either or both 
bones of the forearm, according to the functional character of 
the limb, and the specialization of rotatory radial movements of 
the forearm and hand. Moreover, in forms presenting the origin 
by two heads from the pectoral girdle, either or both of the 
girdle heads may be connected with either, or, by division of the 
insertion, with both of the forearm bones. 
Consequently the analysis of the Biceps muscle would result 
as follows, retaining the names “ glenoid” and “coracoid” as 
designating respectively the outer and inner girdle origins of 
the muscle: 
Complete type form of muscle, four heads. 
1. Gleno-radial. 3. Coraco-radial. 
Gleno-ulnar. 4. Coraco-ulnar. 
This type becomes modified in various forms by reduction 
and elimination of two or more heads, so as to present a number 
of variations. Krause* first pointed out this quadricipital 
character of the human Biceps, based on careful dissection of 
the muscle and analysis of the fibres at the insertion. He also 
collected a number of comparative anatomical facts in support of 
this view of the compound character of the muscle. A by no 
means exhaustive consideration of the structure of the Biceps in 
the lower animals reveals the existence of the following reduc- 
*W. Krause, Specielle und Macroscopische Anatomie, Hanover, 1879, p. 293, 
