1892.] NATURAL SCIENCES OF PHILADELPHIA. 217 



On the Cephalo-humeral Muscle and the so-called rudiviental Clav- 

 icle of Carnivora. — Dr. Harrison Allen spoke of some of the 

 peculiarities of the cephalo-humeral muscle in mammals and invited 

 especial attention to the presence of a small iibro-cartilaginous disc 

 in the junction of the cephalo-humeral with the muscles which are 

 inserted in the bones at the region of the shoulder. This is well 

 defined in Felts and is identihed as a rudimental clavicle. Dr. 

 Allen had detected this structure in Herpestis, Taxklea, Cercoleptes, 

 JBassarls and Frocyon. 



The cartilage is either in the form of a flat disc or a minute 

 scythe-shaped rod, and is constant in lying directly over the 

 greatest convexity formed by the round of the shoulder. It seems 

 to give strength to the centre of a muscle-system of which the 

 cephalic, cervical, pectoral and latissimal sheets are parts. The 

 identification of such a plate or rod with a true clavicle is doubtful 

 since in Balantiopteryx (a genus of bats) the structure above de- 

 scribed is remarkably developed while the clavicle is as well 

 formed as in any other animal. The long rod-like body is con- 

 tinuous with a fascicle of fibres arising from the pectoralis and 

 receives the insertion of the occipito-iJollicalis, The anterior end of 

 the rod lies in the upper border of the wing membrane and is 

 continuous with the fibrous tliread which represents the tendon of 

 tlie occipito-poUicalis as this muscle is defined in the bats generally. 

 From both the proximal and distal divisions of this muscle delicate 

 fascicles pass toward the elbow and the entire plan appears to be 

 associated with the rudiment of the characteristic skin sac. Slight 

 modification of this arrangement is met with in the allied genus 

 Rhynchonycteris. 



Comparison of this arrangement with that seen in the common 

 brown bat (Adelonycteris fuscvs), the noctula bat (^NoctuUnia 

 noctula), and the false vampire ( Vampyrus spectrum) showed that 

 the part taken by the rod in Balantiopteryx is the tendon of a 

 pectoral muscle-fascicle which is inserted into the occipito-j)ollical 

 muscle as it crosses the shoulder, while in the group of the Molossi 

 the muscle-fascicle is fleshy throughout its entire extent, but on 

 the whole preserving the same relations. Thus the fibro-cartilage of 

 Balanteopteryx is represented by fibrous tissue in AdeloHycieris and 

 both these in turn by muscle in the Molossi. Dr. Allen believed 

 that it was inexact to speak of a clavicle and of this rod as things 

 which were equal. The clavicle acts with the scapula in supporting 

 the head of the humerus but in no wise limiting or determining its 

 movements, while the rod is always over the outer aspect of the 

 shaft of the humerus below its head and here acts as a check to 

 abduction of this bone. 



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