23 
THE POULTRY BOOK. 
and naturalists, both of this and other countries, — even those who have most 
recently written on the development, &c., of the chick, — have stated that such is 
the case ; whilst the latest authors on Poultry continue the same error. ‘ The 
tapping which is heard,’ writes the author of ‘Domestic Poultry,’ ‘ and which opens 
the prison doors, is caused by the bill of the enclosed chick ;’ similar language 
being employed by all others. 
“ Though opposed to the many great authorities who have written on this 
subject, and opposed, also, to the adopted views of all, I do not hesitate to assert, 
in contravention, the facts as observed by myself, especially as such facts can be 
so simply and so readily tested and substantiated by every one. 
“Whilst recently engaged in some investigations concerning the young chick at 
various periods of its growth in the egg, I was led to doubt the correctness of the 
common explanation of the (so-called) tapping-like sound, from observing, first, that 
it was so continuous, or prolonged, it being heard for about forty -eight hours before 
a fracture in the egg was made, thus involving an amount of labour and effort on 
the part of the young tenant not commensurate with the small effect produced — a 
small fracture, when the whole remaining circle of the egg could be seen to be 
broken often in from two to six hours ; and, secondly, as the slightest scratch or 
tap with the nail, or similar hard substance, on an egg, produces, when the ear is 
applied, a very much louder sound than that made by the chick, I considered that 
the tapping, if really produced by strokes of the bill breaking the shell, ought to be 
threefold more distinct and louder than they really are. 
“ The facts are simply these : — The so-called repeated ‘ tapping ’ is not caused hy 
the stroke, nor hy any other mode of contact of the chick'' s hill with the shell — it is 
simply respiratory, and produced during the expiration of the breath. Perhaps the 
more homely words, ‘ clicking,’ or ‘ smacking,’ would more accurately define the 
sound ; it exactly resembles that which may be made by puffing small quantities of 
air through the closed lips, as in the act of smoking ; and, indeed, from my own 
observation, I conclude that it is produced in a manner analogous, by the air 
passing, at each expiration, through the lungs of the tender chick. 
“It is further observable that the so-called ‘ tapping’ sound begins to be heard, 
though indistinctly at first, at that very period of incubation at which physiologists 
state that air first enters the lungs, viz. on the nineteenth day, or two days before 
hatching. I also remarked that the sound in question was sometimes heard, not as 
a single, but as a double sound ; the latter of the two being louder than the former, 
and thus corresponding to the expiration and inspiration of the breath. 
“ I perceived that the egg was really broken (at first with a star-like fracture) by 
occasional smart blows with the horny tip of the bill, and which impinged, with no 
inconsiderable power, against the shell, as any one may satisfy himself by placing 
the ear close to the opening just made. At the period of hatching the chick obtains 
great additional space in the egg, by which it is enabled to make enlarged efforts. 
Thus, by the nineteenth day (by which I mean two days before it liberates itself), 
it is seen to occupy the smallest space in the egg ; nearly one-third, at the larger 
