64 COMPARATIVE ANATOMY 



cone is drawn tight into the orifice, and completely 

 closes the breathing canal 1, 1 ; while on the othei 

 hand, the action of the external part of the muscle 

 draws the conical plug forward and upwards, and 

 affords a free passage for the air in respiration. This 

 beautiful structure it is which enables the animal, 

 under the immense pressure to which it is sometimes 

 exposed, to exclude the sea-water from its lungs : so 

 far from the water being forced down the canals, the 

 enormous load serves only more effectually to press 

 down and close the valves that defend the passages 

 to the lungs. (Journal of a Voyage, c. 152.) 



To this w r e may add, that in those genera in 

 which the external aperture to the ear is not covered 

 by the common integuments, there is a valve placed 

 in the passage to guard against the pressure of 

 water upon the drum of the ear, whereby it would 

 be broken and the organ of hearing destroyed. 

 Mr. Scorseby's words, in relation to the Mysticetus, 

 are, there is an elegant appearance found near 

 the external opening, in the shape of a little plug, 

 like the end of the finger, which is inserted in a cor- 

 responding cavity in the interior of the canal, by a 

 slight motion of which the opening can either be 

 effectually shut, for the exclusion of water, or un- 

 closed for the admission of sound : and M. Orbigny 

 remarks, upon four of the P. Griseus which he had 

 an opportunity of examining, " the external orifice of 

 the ear was shut by a very fine valve which appeared 

 to have the power of opening and shutting at the 

 animal's will." (F. Cuviers Hist., c. 185 ) 



