570 



THE MECHANICAL FUNCTIONS. 



a, a, b, b, Fig. 226, as they arise from the two 

 sides of the edges of each lamina : they are 

 exceedingly numerous, above a thousand being 



226 



contained in the space of an inch ; and they are 

 of two kinds, each kind having a different form 

 and curvature. Those marked a, a, which arise 

 from the side next to the extremity of the feather 

 are branched or tufted, and bend downwards, 

 while those marked b, b, proceeding from the 

 other side of the lamina, or that nearest the root 

 of the feather, are shorter and firmer, and do not 

 divide into branches, but are hooked at the ex- 

 tremities, and are directed upwards. When the 

 two laminae are brought close to one another, 

 the long, curved fibrils of the one being carried 

 over the short and straight fibrils of the other, 

 both sets become entangled together ; their 

 crooked ends fastening into one another, just as 

 the latch of a door falls into the cavity of the 

 catch which is fixed in the door-post to receive 



