170 Mr Houston an the Structure and Mechanism 



the blood of the body and tongue. This remarkable cavity between the veins 

 and auricles has never, that I am aware of, been before noticed in this animal 

 The French Academicians have described the auricles as being large, and the 

 left in the chameleon which they dissected was the more capacious ; but they 

 have made no allusion to distinct sinuses apart from the auricles. In both those 

 which I examined, these sinuses were well marked ; the right, however, ex- 

 ceeded by one half in magnitude the left, and formed a larger cavity than 

 both the auricles taken together. It extended the whole length of the chest 

 (Fig. 6, v.), from the superior aperture to the liver, and was not less when 

 distended than two lines in diameter. Both were filled with coagulated 

 blood ; and the texture of their coats appeared the same as that of the veins 

 which emptied into them. Their use may probably be connected with the 

 varying condition of the circulation in the skin, and the erectile portion of the 

 tongue, on which I conceive depend all the phenomena for which these two 

 parts have gained such notoriety. They may serve as reservoirs for the 

 blood, when suddenly abstracted from either of them, previous to its re- 

 admission into the heart. 



After this detailed description of the structure of the chame- 

 leon'*s tongue, we may be enabled to estimate the applicability 

 of the several theories, which have from time to time been ad- 

 vanced, to account for its peculiar powers of motion. 



It was denied by Marmol, who examined many chameleons 

 for the purpose of clearing up this point, that their tongue had 

 any such powers at all. He assures us that it is never exercised 

 as a trap for insects, and that any thing which he had observed 

 of the animal, would not induce him to change his opinion, that 

 air and the sun's rays are its only nutriment*. 



M. Perrault attributed the elongation to an expiratory effort 

 of the animal, which darted its tongue from its mouth, " com- 

 rae si il la crachoit avec violence" -f. The great size of the 

 lung he supposed was for the purpose of effecting this move- 

 ment. But there is no circumstance connected with the anato- 

 my of the organ, or its mode of advancement,, to countenance 

 this explanation. Besides, the chest during the act, in place of 

 evincing the motions attendant on an effort of expiration, re- 

 mains dilated and immoveable : respiration for the moment ap- 

 pears to be suspended. 



M. De la Hire suggested that perhaps the state of the rest of 

 the tongue is that in which it exists when elongated, and in 



• See Mem. de I'Acad. Roy. des Scienc t. 3. Ire. partic, p. 47. 

 t Ibid. T. 9, p. 156. 



