THE POULTRY BOOK. 
17a 
to solsct tliosG cliickens that will be well crested, immediately on their emerging 
from the shell. Perhaps the most extraordinary circumstance connected with this 
swelling is, that it contains by far the greater part of the brain — being, in fact, a 
protuberance of the frontal or forehead hone ; even in old fowls, however, this tuber 
rarely becomes entirely bony, hut consists in great part of membrane : hence there 
is no protection for the brain beyond the feathers of the crest and the integuments; 
so that a slight blow on the head, that v/ould not affect an ordinary bird in the least,, 
will destroy a Polish fowl. 
The peculiar structure of the skull of these crested fowls, was noticed as long 
since as 1656, being described by Peter Borelli, in his Histor. et Observat. 
rarior.,” page 154, and formed the subject of a chapter by the celebrated Blu- 
menbach, v/ho, in his work entitled Be Anomalis et Yitiosis Quibusdam Nisus 
Formativi Aberrationibus Commentatio. Gottingae 1813,” writes : — 
“ Those forces which act on the configuration of bones, may be observed in that 
aberration of the formative nisus by which the primitive stock of animals de- 
generates into constant and hereditary varieties. 
As a sample of these, I may mention the remarkable variety of domestic 
poultry which are distinguished by a thickly feathered crest on the head and by a 
ball-like protuberance of the forehead connected with it. 
After having subjected to the dissecting knife, and carefully compared with each 
other, numerous heads of this variety at different ages, I think I have discovered 
that the principal cause of the wonderful change of form is to be found in the tight 
transverse construction of the integuments of the head. By this, the region of the 
skull beneath is hindered to such a degree from its normal increase, that the brain 
itself is tightly constricted, so that being pressed in front and raised upward, it, as 
it were, inflates the fore part of the skull into a bony ball; the occipital part of it, 
on account of the smaller increase of the cerebellum, appears more depressed ; 
the skull itself, however, thus wonderfully inflated, becomes thinner than is usual 
in other poultry. 
“It is well known, moreover, that this serious alteration of form in the brain 
exerts an influence on the intellectual faculties of these fowls ; they are almost 
always, though in various degrees, stupid, and, as it were, without intelligence. 
“ What w'e have observed above concerning the aberrations of the formative 
nisus, namely, that it occurs less frequently in animals of the male sex than 
in females, is confirmed by the examples of this variety of poultry distinguished 
by the protuberance on the head ; for of this deformity very slight traces indeed 
are found in the cocks, and those but seldom. 
“It is surprising that Pallas should have thought it probable that this variety 
of poultry, affected with the ball-like formation on the forehead, has been pro- 
duced by a cross of the Numidian Meleagris with the common poultry : this 
opinion, not to mention other things plainly contrary to it, is easily refuted on 
careful dissection, by a comparison of the horned head of that bird with the 
skulls of the crested poultry. For in the Meleagris that small conical and com- 
