THE PIGEON. 213 



anterior (dorsal) surface of the tarso-metatarsus and on the 

 dorsal surface of the toes. 



XVII. 1 In one of the large quill feathers make out the 

 following points : 



142. The stem, or scapus, consisting of a proximal 

 portion, the tube or calamus, which is cylindrical and 

 hollow or nearly so, and of a distal portion, the shaft or 

 rachis, which is somewhat quadrate in section, grooved on 

 its ventral 2 side, and formed internally of a white, pith-like 

 substance. 



143. The barbs, delicate tapering processes, flattened in 

 a direction at right angles to the long axis of the feather and 

 attached in two rows one on each side of the rachis : they 

 constitute, taken together, the vane or vexillum of the 

 feather. 



144. The inferior umbilicus, a small aperture at the 

 proximal end of the calamus, by which the feather-papilla 

 enters the latter. t 



145. The superior umbilicus, a small oblique aperture 

 at the junction of the calamus and rachis, putting the 

 cavity of the former in communication with the exterior. 



XVIII. Cut off a small piece of the vane and examine it under a 

 moderately high power of the microscope, taking care to 

 distinguish between the dorsal and ventral surfaces, and the 

 proximal and distal ends of the piece. It is advisable to soak 

 the fragment for a short time in alcohol, so as to remove the 

 air, and then to examine in glycerine. Note : 



146. The barbules, small pointed processes, attached obliquely in two 

 rows one on each side of the barbs, to which they are related in the 

 same way as are the latter to the rachis : they are so disposed that the 



1 It will probably be found convenient, in practice, to omit Sections 

 XVII XIX until the dissection of the soft parts is completed, and to 

 proceed from 141 to Section XX., p. 214. 



2 That is, the lower side in the case of the remiges and rectrices, or 

 the inner side in the case of the ordinary contour feathers. 



