172 Ml* Houston 07i the Structure and Mechanism 



fingers are unavailing. Its cupped extremity admits of being 

 spread out a little, but neither before nor after death can its 

 form or bulk undergo any greater change. The protrusion of 

 the style of the os hyoides from the mouth will be found, on 

 studying its form and connections, an equally inefficient cause. 

 The Baron compares this part of the process to that accom- 

 plished by the tongue of the woodpecker. He says*, " II 

 pent s'alonger considerablement par un mechanisme analogue a 

 celui qui a lieu dans les pics." But the diffi2rence in the fornj 

 and arrangement of the os hyoides and its muscles in the two 

 animals, will not sanction a comparison of their actions to an ex- 

 tent which would account for the phenomenon. In the wood- 

 pecker, 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 for- 

 wards as the upper mandible, into a groove of which they en- 

 ter. Muscles which arise from the chin, and follow the course 

 of these cornua to their very points, have the power of retract- 

 ing them, and in the same proportion of propelling the tongue, 

 which is a solid continuation of them, out of the mouth. 

 Whereas in the chameleon, whose tongue can be projected even 

 farther than that of the woodpecker, the cornua of the os hyoi- 

 des are not so much as an inch long, and the space they have 

 to move in is so limited, that the muscles extending from them 

 to the lower jaw could not, by pulling them forwards, advance 

 the tongue out of the mouth more than half an inch. Since 

 then, the structure of the prehensile portion of the tongue will 

 not admit of its elongation ; and since also the point of the style 

 cannot be advanced from the mouth more than half an inch, to 

 which two circumstances alone the Baron attributes the protru- 

 sion of the organ, it is evident that his explanation is incom- 

 plete, inasmuch as it does not account for its usual propulsion 

 to the distance of five, six, or seven inches. 



Having thus passed under review the several theories ad- 

 vanced in explanation of this remarkable process, and shown 

 their respective insufficiency to that end, I venture to offtr one 

 which to me appears not only unobjectionable, but adequate to 



• Ibid. T. 2. p. «81. 



