176 Mr Houston on the Siritcture and Mechanism 



momentary, and observed during a very short stage of the pro- 

 cess. The progress of the tongue on leaving the mouth was at 

 first slow, and became gradually accelerated as it approached 

 near the prey, when it shot forwards with remarkable quickness, 

 — a mode of proceeding much more likely to ensure success than 

 if it had advanced with uniform rapidity from the commence- 

 ment. This quickness perhaps equalled that which is attri- 

 buted to the organ when in vigour ; but it was only manifested 

 after its gradual repletion with blood, and when a slight impulse 

 was sufficient to produce it. 



Should the explanation which I have given of the mechanism 

 of the chameleon's tongue, founded on its structure and appear- 

 ance during life, be admitted as applicable to the animals on 

 which I have made ray observations, it may be likewise to all, 

 however vigorous, for the same cause must equally produce the 

 elongation whether the act be rapid or slow — whether it take 

 place during a state of activity or weakness. 



Several individuals who have witnessed the change of colour 

 and mode of feeding of my chameleons, can corroborate the ac- 

 curacy of the above statements ; but I shall particularly refer 

 for evidence of it to ray friend Mr Tagert, who took a particu- 

 lar interest in observing their habits ; and who, even while the 

 animals were alive, agreed with me in the opinion, which I hope 

 mv after dissections have sufficiently established, regarding the 

 cause of elongation of the tongue. 



Most of the preparations from which the drawings were taken 

 I have preserved, and placed in the Museum of the Royal Col- 

 lege of Surgeons. 

 31. York Street. 



EXPLANATION OF THE PLATE. 



Fig. 1st.— The Os Hpoides. 



A The Style. BB The anterior cornua and cartilaginous puUy. CC The 

 posterior coniiia. hhh The internal cerato-maxillary muscle. 



Fig. 2d The Muscles. 



C The posterior cornua of the os hyoides. D Lower jaw. a Sterno-hyoid, 



3 



