26 
differentiated from the “humeral” or “ abdomino-humeral ” panni- 
culus. i 
Adopting Windle’s* convenient classification of the pectoral group 
of fibres, | may say that pectoralis A is a “ superficial manubrial,’”’ or 
rather “ manubrio-clavicular;’’ pectoralis B is a “gladiolar,” fused 
with a superficial lamella of a “ costal”? segment; that pectoralis C is 
a deep “ costal” segment; and that an “abdominal ” segment is repre- 
sented by the abdomino-humeral panniculus, no special pectoralis 
quartus being present distinct from the latter. Upon the question of 
the morphological relations of the pectoral muscles to the panniculus, 
c.f., also paper by Parsons upon the myology of rodents ;+ this author 
regards the pectoral mass as differentiated from the panniculus. 
With regard to the attachment of the humeral panniculus it may be 
noted that the dorsal end of the tendinous arch described above pos- 
sesses no definite attachment to bone. It is traceable dorsally under 
cover of the latissimus, which there overlaps the humeral panniculus as 
the latter enters the axilla. It is doubtless the homologue of the 
achselbogen so commonly present in mammals, such as, for example, 
MacCormick{t notes in Phalangista, which there, as in Notoryctes, 
receives fibres of the panniculus, and in Phalangista also fibres of the 
pectoralis quartus. If we are to look upon part of the panniculus 
fibres in Notoryctes as those of a pectoralis quartus, then the fibres of 
the latter muscle are not inserted along with or close to those of the 
pectoralis major as in Cuscus, Thylacinus, and Phascogale,§ and in 
Phalangista vulpina,|| but, like the fibres of MacCormick’s ‘“ ventro- 
humeral”? muscle (true pectoralis quartus?), are blended with the 
tendon of the pectoralis minor. 
The question of the homology of the pectoralis quartus has been the 
subject of much discussion by many writers, and it is certain that 
various pectoral and axillary muscles have indifferently received this 
name. Windle concludes his discussion of the subject by remarking 
that “the diverse views held by authors who have been cited, and 
by others who might have been mentioned, with regard to pectoralis 
quartus and achselbogen, are many of them reduced to an agreement, 
by what I believe to be a right comprehension of the so-called panni- 
culus of the abdomen, namely, that it is the hindermost portion of 
the members of the pectoral group.” I cannot think that this is a 
satisfactory mode of statement, and I should incline rather to accept 
Prof. Cunningham’s% view in reference to axillary muscles generally, 
that in that region “there is not the same sharp, well-defined subdi- 
vision between the panniculus and the deeper stratum that exists 
elsewhere.” 
For a general survey of the arrangement of the elements of the 
pectoral group of muscles in various mammalian orders I would simply 
refer to Windle’s comprehensive sketch in the memoir already quoted 
from.** 
M. subscapularis (figs. 6 and 7, sbs.). A comparatively broad 
and triangular muscle, whose fibres are arranged in a bipenniform 
manner. Its fibres arise from the venter or inner aspect of the 
*Ixvii., page 349. +xlvili., page xet seg. +xxxvi., page 112. §xxi., 
page 7. .'||xxxvi., page 112. 4 v., page 385. ** Ixvii. 
