PIGEON. 23 



PIGEON. 



Class — Aves. Order — Carinatse. Type — Columbus (Pigeon). 



Body covered with feathers, which are a modification of the 

 epidermis. Take one of the larger feathers and examine for the 

 following parts : — 



(1) A central axis — the seapus — forming the stem of the 



feather, and divided into a lower hollow part — the calamms 

 or quill — where its base is implanted in a small sac of the 

 cutis vera. 



(2) A rachis or shaft, which is four-sided, and is simply a con- 



tinuation of the calamus ; and 



(3) The shaft which carries the lateral processes (barbs) of the 



feather, collectively forming the vexill/wm. 



The calamus at its lower end has an aperture, through which 

 the pulp holding blood-vessels enter the shaft. The barbs are 

 narrow processes, which at their free end taper to a point, and at 

 their bases are attached to the rachis. The margin of the barbs 

 are furnished with smaller processes, which form an open angle 

 with the barb, and hold the same relation to the barb as the barbs 

 do to the rachis. The extremities of the barbules are hooked, so 

 that the opposed margins of the barbs interlock together through 

 the medium of these barbules. 



Each feather sac — into which the lower end of the calamus is 

 fitted — is provided with small muscles, which by their contrac- 

 tion can elevate the feathers. In the integument over the coccyx 

 is the uropygial or oil gland — this is a modification of a sebaceous 

 gland, and secretes an oily liquid, which the pigeon covers its 

 feathers with in the act of preening. 



Note the position of the external nares, which are placed at the 

 sides of the upper mandible. They are wide and freely open, to 

 allow of easy ingress of air during respiration. The nasal 

 passages communicate with the palate and pharynx by two 

 distinct but contiguous apertures : a bristle should be passed 

 through the external nares to verify this. The external meatus 

 of the ear is seen behind and somewhat below the eye ; and, by 

 careful inspection, a fold of the integument may be seen project- 

 ing from the fore part of the meatus. 



Notice the third eyelid or nictitating membrane. 



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