164 Mr Houston on the Structure and Mechanism 



the mouth, though somewhat more tardily than in its advance ; 

 and whenever the elongation had been considerable, its ex- 

 tremity was bent a little downwards, giving to the organ a 

 slightly curved appearance. When projected, the tongue ac- 

 quired a thickness equal to the largest swan''s quill, and a 

 length not less sometimes than six or seven inches. Its consis- 

 tence I attempted, on one occasion, to ascertain, by catching 

 it between my fingers, when it imparted the feel of an elastic 

 body, yielding slightly when pressed on, and springing back 

 instantly to its former state as soon as the pressure was re- 

 moved. The experiment caused only a short delay to its 

 progress, but neither altered its form or course, nor unfastened 

 the prev from its extremity. Its colour along the centre was a 

 dark livid ; and each side, to within about an inch of the ex- 

 tremity, presented a whitish band, which, during the act of 

 elongation, was straight and uniform, but in the retraction of 

 the organ became evidently tortuous and wrinkled ; while the 

 whole surface, both centre and sides, was irregularly streaked 

 with innumerable very minute blood-vessels. Near the ex- 

 tremity, a few veins much larger than the others, and having 

 a longitudinal course, were in the highest state of turgescence. 



It seems probable that the tongue is the sole agent assigned 

 to the chameleon for obtaining its sustenance. Flies have of- 

 ten rested on every part of its body, and though it has looked 

 wistfully at them, it had no means of apprehending its annoyers. 

 I have frequently observed them for a considerable time on its 

 very lips without any attempt being made at their seizure. 

 Even when placed before it, if not sufficiently distant to afford 

 room for the necessary evolution of its tongue, the chameleon 

 was under the necessity of retiring, or raising back its head for 

 the purpose. 



It would appear to possess the power of regulating the force 

 of propulsion of its tongue according to the distance of the 

 prey ; for when the latter lay near to the mouth, the organ ad- 

 vanced on it slowly ; when farther off its velocity was more 

 marked ; and whether nearer or more remote it invariably 

 darted with greatest quickness as its point approached the ob- 

 ject. 



The chameleon, when vigorous in its natural climate, is said 



