THE POULTRY BOOK. 
29 
end, is at this time filled with air only ; but now, by its frequent struggling efforts, 
the chick gradually works itself up till it fills the whole space ; and by this partial 
unpacking, as it were, of itself, acquiring more liberty for action. 
On pressing the egg against the ear it will be found that the young chick 
breathes, when first heard, about eighty times in a minute, as denoted by the 
‘ tapping,’ or respiratory sound ; but afterwards generally not more than sixty. It 
makes the struggling efforts five or six times per minute, while the sharp strokes 
with the hill, by which it breaks the shell, are repeated at unequal intervals of from 
one to five minutes : I perceived that sometimes these strokes were repeated in 
immediate succession. The action of the heart is so rapid that it cannot he counted 
with accuracy. 
“ The chick gradually works itself round in the shell during its struggles, break- 
ing it in its progress, till at length the lid-shaped upper portion of the shell is 
detached. In this process the ‘ tapping,’ or breath sound, generally, though not 
always, continues ; and any one may, at this stage, satisfy himself by observation 
that it is only by the occasional blows with the hill, suddenly and forcibly made, 
and generally at the commencement or at the termination of the struggle, that the 
shell is broken. 
“ I shall now detail the simple expedients by which I proved that the * tapping’ 
was not caused. ‘ by the contact of the chick’s hill with the shell.’ 
“ I broke a small hole in the round end of the egg, when the * tapping ’ was 
distinctly audible. M. Keaumur, unluckily, attempted to satisfy himself as to the 
cause of this sound by holding the egg before the light of a candle ; had he broken 
a hole in the shell, when he examined it, he would have avoided his error. By 
this means I saw the hill in situ, and plainly perceived that, though the sound 
continued, the bill itself did not come in contact with the shell. Nay, in some 
early instances, the sound was heard before the hill was visible, or had protruded 
through the enveloping membrane. To satisfy myself again I watched in other 
examples, till a small fracture had been made in the shell by the chick ; this breach 
I then enlarged considerably, breaking away the shell so as to bring the bill of the 
chick into open view — to isolate it, indeed, and to pi'event the possibility of its 
coming in contact with the shell — still the same ‘tapping’ sound continued as 
before, and, as I now clearly saw, was produced solely by the breathing of the chick. 
Further remark would he wholly superfluous. 
“ It appears to me probable that the reduction in the frequency of the tapping or 
noisy respiration, soon after I had made an enlarged opening in the shell, was 
dependent upon the free admission of the pure atmospheric air, by the vivifying 
influence of which the respiratory organs speedily gained a more perfect and normal 
action. In some cases the sound ceased for a while, when a free aperture had thus 
been made ; and the chick gaped widely and repeatedly, as if expanding its lungs 
with air. In the weakest chickens I generally found that the respiratory sound was 
most continuous ; indicative, I conceive, of less power in the respiratory organs to 
gain a more perfect action. 
