354 



ZOOLOGY 



SECT. 



feather papilla. A second, extremely minute aperture, the superior 

 umbilicus (sup. umb.\ occurs at the junction of the quill with the 

 vane on the inner or ventral face of the feather, i.e., the face 

 adjacent to the body. A small tuft of down in the neighbourhood 

 of the superior umbilicus represents the after-shaft of many Birds, 

 including some Pigeons (vide infra). 



The vane has a longitudinal axis or rachis (rch.) continuous 

 proximally with the quill, but differing from the latter in being 

 solid. To each side of the rachis is attached a kind of membrane 

 forming the expanded part of the feather and composed of barbs 

 delicate, thread-like structures which extend obliquely outwards 



FIG. 965. Structure of Feather. A, small portion of feather with pieces of two barbs, each 

 having to the left three distal barbules, and to the right a number of proximal barbules, many 

 of them belonging to adjacent barbs. B, Booklet of distal barbule interlocking with flange of 

 proximal barbule. C, two adjacent proximal barbules. D, a distal barbule. (From Headley, 

 after Pycraft.) 



from the rachis. In an uninjured feather the barbs are closely 

 connected so as to form a continuous sheet, but a moderate amount 

 of force separates them from one another, and it can readily be 

 made out with the aid of a magnifying glass that they are bound 

 together by extremely delicate oblique filaments, the barbules, 

 having the same general relation to the barbs as the barbs them- 

 selves to the rachis. 



The precise mode of interlocking of the barbs can be made out 

 only by microscopic examination. Each barb (Fig. 965, A) is a 

 very thin and long plate springing by a narrow base from the 

 rachis, and pointed distally. From its upper edge the edge 



