268 Mr W. Macgillivray on the Covering of Birds. 



and lateral surfaces, along the edge of the latter. The direction 

 of the barbs is obliquely outwards with respect to the shaft, 

 that is, inclining more or less at an acute angle toward the tip 

 of the shaft. Each barb is flattened or compressed vertically 

 with reference to the shaft, considering it horizontal with its 

 face downwards, concave on the side next the tip, convex on the 

 other, so as to fit to its neighbour on either side. It terminates 

 at its lower part, or that on the concave surface of the feather, 

 in a sharp edge, generally diaphanous, which is reflected in the 

 direction of the tip of the feather. The body or substance of 

 the barb is pretty uniform in thickness, and it is only when 

 viewed in connection with the barbules that it could with any 

 propriety be said to be triangular. 



From the upper part or edge of each barb there proceed two 

 sets, one on either side, of minute filaments, having a direction, 

 with respect to the barb, similar to that of the barbs with re- 

 spect to the shaft. These smaller filaments are named barbules, 

 barbula, les barbules. It is by means of them that the barbs are 

 firmly kept in apposition. The manner in which this is done, is 

 not by the barbules of one barb interlocking with those of another, 

 in the manner of dovetailing, or as the teeth of two combs might 

 be made to alternate by mutual insertion, as I believe is generally 

 supposed. The position and direction of the barbules do not 

 admit of such union, seeing they meet each other at an angle, 

 and therefore cannot interlock, which could only happen were 

 they to meet vertically. The barbules of the side next the tube 

 are shorter and more adpressed ; those of the side next the tip 

 of the feather are longer and more patulous. The latter are 

 curved downwards at the extremity, while the former are curved 

 upwards ; and being placed in apposition they form two distinct 

 and continuous edges, the incurvate or anterior series of one 

 barb overlapping and hooking into the recurvate posterior series 

 of the barb next to it. Although the connection of the barbs 

 may not be easily seen in the ordinary feathers, yet it may in 

 general be discovered in the quills and tail-feathers, without the 

 aid. of a glass. When the barbs are pulled asunder in the plane 

 of the web, their cohesion is found to be very considerable in 

 most feathers. When the posterior barb is pulled downwards 

 out of the plane of the web, the cohesion is found still greater ; 



