462 



MANUAL OF ZOOLOGY 



which it subsequently protrudes as an elongated feather-germ, 

 its vascular dermal interior being the feather-pulp. The 

 horny substance of the feather is formed from the epidermis 

 of the feather-germ. 



The feathers do not spring uniformly from the whole sur- 

 face of the body, but from certain defined areas (Fig. 275), 



Fig. 275. — Pterylosis of Columba livia. A, ventral; B, dorsal. al. pt, alar 

 pteryla or wing-tract; c. pt, cephalic pteryla or head-tract; cd. pt, caudal 

 pteryla or tail-tract; cr pt, crural pteryla; cr. apt, cervical apterium or neck- 

 space; fm. pt, femoral pteryla; hu. pt, humeral pteryla; lat apt, lateral 

 apterium; sp pt, spinal pteryla; v. apt. ventral apterium; -' M. ventral Dtervia 

 (After Nitsch.) v y 



the feather tracts or pteryla; (sp.pt, hu. pt, etc.), separated 

 from one another by featherless spaces or apteria (v. apt, 

 etc.), from which only a few filoplumes grow. 



In the wings and tail certain special arrangements of the 

 feathers are to be distinguished. When the wing is stretched 



