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MANUAL OF ZOOLOGY 



which it subsequently protrudes as an elongated feather-ge?-m, 

 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 Columha livia. A, ventral; B, dorsal. at 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; Im. fit, humeral pteryla; lat. apt, lateral 

 apterium; sp.pt, spinal pteryla; v. apt, ventral apterium; v. pt, ventral pteryla. 

 (After Nitsch.) 



the feather tracts or pterylce (sp.pt, hit. 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 



