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circumftance arifes from the fuperior ftrength of the 
mufcles of the larynx. 
I procured a cock nightingale, a cock and hen 
blackbird, a cock and hen rook, a cock linnet, as 
alfo a cock and hen chaffinch, which that very emi- 
nent anatomift, Mr. Hunter, F. R. S. was fo oblig- 
ing as to diffeft for me, and begged, that he would 
particularly attend to the ftate of the organs in the 
different birds, which might be fuppofed to contri- 
bute to finging. 
Mr. Hunter found the mufcles of the larynx to be 
ffronger in the nightingale than in any other bird. of 
the fame fize; and in all thofe inffances (where he 
difle&ed both cock and hen) that the fame mufcles 
were ffronger in the cock. 
I fent the cock and hen rook, in order to fee 
whether there would be the fame difference in the 
cock and hen of a fpecies which did not ling at all. 
Mr. Hunter, however, told me, that he had not 
attended fo much to their comparative organs of 
voice, as in the other kinds ; but that, to the beff of 
his recollection, there was no difference at all. 
Strength, however, in- thefe mufcles, feems not 
to be the only requifite ; the birds muff have alfo 
great plenty of food, which feems to be proved 
fufficiently by birds in a cage ffnging the greateft part 
of the year, when the wild ones do not (as 1 ob- 
ferved before) continue in fong above ten weeks. 
The food of linging birds conlifts of plants, in- 
fects, or feeds, and of the two firft of thefe there is 
infinitely the greateft profufion in the fpring. 
As for feeds, which are to be met with only in the 
autumn, I think they cannot well find any great 
quantities 
