450 Mr. W. P. Pycraft on the Pterylography fyc. 



patagii and deltoid, it passes upwards over the base of the 

 neck, and at the same time expands to form a broad sheet of 

 muscle triangular in shape, and split up to form some half- 

 dozen narrow bands separated by narrow interspaces one 

 from another. These are inserted in the skin along the inner 

 border of the cucullaris dorso-cutaneus. Action : all these 

 strands slope tailwards, so that their contraction draws the 

 skin forwards. 



Pectoralis abdominalis. — This muscle we must regard as 

 divided into two parts, corresponding to the jwrs anterior 

 and pars posterior of Fiirbringer — the subcutaneus thoracis 

 and subcutaneus abdominalis of Gadow. 



The pars posterior arises from the pubis in the usual 

 manner, but in the form of an extremely delicate tendinous 

 band, which, near the middle of the abdomen, becomes 

 suddenly fleshy and is inserted into the free end of the outer 

 branch of the pteryla ventralis. 



The pars anterior is two-headed. The more caudad 

 answers to the normal head and arises from the dorsal 

 border of the pectoralis near its sternal edge. The second 

 head arises cephalad of this, from the external fibres of the 

 2>ectoralis major at the axilla ; the two heads fuse to form a 

 broad band inserted into the dorsal border of the outer 

 branch of the jrteryla ventralis. 



Action : These two muscles owe their independence to 

 the suppression of the band at its middle ; thereby greater 

 facilities arc gained for raising and depressing the long 

 pectoral plumes in display. Contraction of the pars posterior 

 depresses the plumes : conversely, by the contraction of the 

 two heads of the pars anterior these plumes would be raised 

 and at the same time drawn upwards and thrown slightly 

 forwards. 



Serratus superficialis pars metapatayialis. — This is a long 

 band-like muscle arising ventrad of the serratus superficialis 

 posterior, from the base of the uncinate of the fourth 

 thoracic rib ; extending upwards and forwards it is inserted 

 into the hinder end of the pteryla humeralis instead of con- 

 tinuing its course outwards to the elbow. 



