238 



ANATOMY OF VERTEBEATES. 



increases in length , 

 acquiring a more 



114 



\ir 



m 



capsule^ a bulb, and intermediate membranes which mould the 

 secretion of the bulb into its appropriate form. The matrix is at 

 first an extremely minute cone, attached by a filamentary process 

 to a follicle or papilla of the skin ; but it is not a developement of 

 that part, being of a different structure and adhering to it by a 

 small part only of its circumference. The matrix j^i'ogressively 

 its base sinking deeply into the corium, and 

 extended connection by enlarged vessels and 

 nerves, while its apex protrudes to a greater or less extent from 

 the surface of the integument, when the capsule drops off to give 

 passage to the feather which it incloses, and the formation of which 

 has, in the meanwhile, been gradually proceeding 

 from the apex doAvnward. The capsule of the 

 matrix, «, a, fig. 114, is composed of several 

 layers, the outermost of which is of the nature 

 of epiderm; the inner ones are more compact 

 and pulpy. The sides of the capsule which 

 correspond to the outer and inner sides of the 

 grooving feather Avithin are indicated by a white 

 longitudinal line. 



The axis of the capsule is occupied by a me- 

 dulla or bulb, ib. e, also of a cylindrical form, 

 and of a soft fibrous texture, adhering by its base 

 to the parts beneath, and there receiving nume- 

 rous bloodvessels and a nerve. 



Between the medulla and the capsule there are 

 two parallel membranes, one internal, ib. d ; the 

 other external, ib. b ; from the latter membrane 

 a number of close-set parallel laminte extend 

 obliquely from one of the white longitudinal lines 

 above mentioned to the other on the opposite side 

 of the cylinder. The two membranes seem to 

 be united together by the oblique septa. In the 

 long and narrow spaces between these septa, the matter of the 

 vane, ib. c, is deposited and formed into barbs and barbules. The 

 deposition of the material of the barbs commences at the apex of 

 the bulb, and the stem is next formed in the following manner. 



The external longitudinal line from which the oblique laminae 

 are continued, receives and moulds on the inner surface of the 

 external capsule tlie horny covering of the back of the feather, 

 or that lonoritudinal band to the two sides of which the barbs are 

 attached ; and on the opposite surface of the internal membrane 

 are formed the pith or substance of the shaft, and the horny pellicle 



IVratrix of a growing 

 featlier, with the cap- 

 sule laid open. Li'. 



