78 



ANIMAL PHYSIOLOGY. 



[LESSON 26. 



cle is so vascular that the bulb of the hair becomes red in a minute 

 injection, no vessels, however, being visible. The follicle of a feather, 

 on the contrary, is not only abundantly supplied with capillary blood- 

 vessels, but more, the cellular medulla is intensely vascular. In 

 other animals, as will be hereafter seen, when a hair is pulled out, it 



FIG. 115. 



FIG. 116. 



Featherof a canary 

 bird. 



Feather of a Eook injected. 



bleeds; proving a tendency to vascularity in 

 this tissue, which, for all we yet know, may really 

 exist. This will be best understood by consult- 

 ing Fig. 115, which shows the feather of a Rook, 

 the medulla of which is beautifully injected. 



The arrangement of the capillaries will be seen 

 to be peculiar, and characteristic; they are large, 

 as compared with human capillaries, to enable them to transmit the 

 larger-sized corpuscles of the blood. The corticle substance of the 

 feather is marked a, the vascular medulla b. 



425. But feathers differ from hair in 

 another respect; the quill (a), termi- 

 nating in a shaft (5), (Fig. 116), is co- 

 vered on two sides by a feathered por- 

 tion called the vane (c). The feathers 

 of the vane are lamellated, or composed 

 of a series of distinct plates called 

 barbs (c); (Figs. 116, 117, d), these 

 barbs are made up of still smaller barbs, 

 called, therefore, barbules (e), (Fig. 117); 

 and these are found to be provided with 

 a series of very minute barbs or hooks, 

 hence called barbulince a still further 

 diminutive (Fig. 117, /). 



The latter are slightly hooked, to 

 Barb of a feather magnified. enable them to attach the barbules to 



