192 



the result of muscular action. With regard to the elongation ' or 

 shortening of its prehensile portion, which he conceives may be 

 produced by the annular and retractor muscles,* a reference to my 

 account of its structure will show that no such change in its form 

 can take place. A dense, fibrous, inelastic sheath which surrounds it 

 must effectually prevent an alteration being made either in its length 

 or thickness by any muscular force which it possesses. Even when 

 removed from the body, attempts to stretch it with the fingers are 

 unavailing. Its cupped extremity admits of being spread out a 

 little, but neither before nor after death can its form or bulk un- 

 dergo any greater change. The protrusion of the style of the os 

 hyoides from the mouth will be found, on studying its form and con- 

 nections, an equally inefficient cause. The Baron compares this 

 part of the process to that accomplished by the tongue of the wood- 

 pecker. He says-f-, " II pent s'alonger considerablement par un 

 mechanisme analogue a celui qui a lieu dans les Pics." But the 

 difference in the form and arrangement of the os hyoides and its 

 muscles in flie two animals will not sanction a comparison of their 

 actions to an extent which would account for the phenomenon. In 

 the woodpecker the cornua of the os hyoides are remarkably long 

 and curved ; they at first descend in the neck for some way ; then 

 turn up in a loose sheath over the occiput, and pass as far forwards 

 ^s the upper mandibule, into a groove of which they enter. Muscles 

 which arise from the chin, and follow the course of these cornua to 

 their very points, have the power of retracting them, and in the 

 same proportion of propelling the tongue, which is a solid continua- 

 tion of them, out of the mouth. Whereas in the chameleon, whose 

 tongue can be projected even farther than that of the woodpecker, 



• Le9ons d' Anatomic Comparee, T. 3, p. 273, 274, 

 f Ibid. T.2. p 6SI. 



