COMPARATIVE ANAlOMY. 
125 
is sometimes, I believe, called, the vane. By the beards 
are meant, what are fastened on each side of the stem, and 
what constitute the breadth of the feather; what we usual¬ 
ly strip off, from one side or both, when we make a pen. 
The separate pieces of laminae, of which the beard is 
composed, are called threads, sometimes filaments, or rays. 
Now the first thing which an attentive observer will remark 
is, how much stronger the beard of the feather shows it¬ 
self to be, when pressed in a direction perpendicular to its 
plane, than when rubbed, either up or down, in the line of 
the stem; and he will soon discover the structure which 
occasions this difference, viz. that the laminae, whereof 
these beards are composed, are flat, and placed with their 
flat sides towards each other; by which means, whilst they 
easily bend for the approaching of each other, as any one 
may perceive by drawing his finger ever so lightly upwards, 
they are much harder to bend out of their plane, which is 
the direction in which they have to encounter the impulse 
and pressure of the air, and in which their strength is 
wanted and put to the trial. 
This is one particularity in the structure of a feather; 
a second is still more extraordinary. Whoever examines 
a feather, cannot help taking notice, that the threads or la¬ 
minae, of which we have been speaking, in their natural 
state unite; that their union is something more than the 
mere apposition of loose surfaces; that they are not part¬ 
ed asunder without some degree of force; that nevertheless 
there is no glutinous cohesion between them; that, there¬ 
fore, by some mechanical means or other, they catch or 
clasp among themselves, thereby giving to the beard or 
vane its closeness and compactness of texture. Nor is this 
all: when two laminae, which have been separated by acci¬ 
dent or force, are brought together again, they immediately 
reclasp; the connexion, whatever it was, is perfectly re¬ 
covered, and the beard of the feather becomes as smooth 
and firm as if nothing had happened to it. Draw your fin¬ 
ger down the feather, which is against the grain, and you 
break probably the junction of some of the contiguous 
threads; draw your finger up the feather, and you restore 
all things to their former state. This is no common con¬ 
trivance : and now for the mechanism by which it is ef¬ 
fected.* The threads or laminae above mentioned, are in- 
* By the aid of the microscope it appears, that the laminae are not flat, 
as they ajjpear to the unassisted eye, but are semi-tubular, having on 
their outward edge a series of bristles, termed in the text fibres, set in pairs 
opposite one another, which clasp with the bristles of the approximate 
L* 
