ANATOM'S OP BALDEN OPTEE A EOSTEATA. 
241 
the musculo-tendinous diaphragm, and thus forcibly diminishing in every direction the 
capacity of the thorax ; this action, from the great mobility of the ribs, their non-attach- 
ment anteriorly, and the obliquity of their position, can in these animals be carried to an 
extent proportionally greater than in any other mammals. Whilst this is being accom- 
plished the entire larynx is drawn forwards and elevated, and the posterior and internal 
lips of the arytenoid bodies being at the same time brought into contact, form by being 
overlapped and covered by the flexible margins of the epiglottis a protrusible tube ; in 
this state the upper opening of the glottis is extended into the pharyngeal orifice of the 
nares. The elevation of these parts appears to be accomplished in the following 
way: — First, the styloid bones or great cornua of the os hyoides are drawn upwards 
and fixed by the action of the stylohyoid muscles ; next, the body of the hyoid bone is 
raised and carried forwards by the hyokeratic and kerato-pharyngeal muscles, whose 
combined action is to approximate the body to the cornua; and finally, the stylopha- 
ryngeus, constrictor and hyoepiglottic muscles draw forwards the glottis, whose tubular 
shape is preserved by the arytenoepiglottideus muscles approximating the lateral and 
free margins of the arytenoid bodies on each side to the epiglottis in front of them, the 
edges of the latter overlapping those of the former. This being accomplished, the pala- 
tine muscular fibres situated round the nasopharyngeal orifices contract and grasp the 
intruded glottis, and so by this beautiful and simple contrivance a free and direct channel 
of communication is formed between the lungs and the external orifices of the blow- 
holes. While these actions are in progress the palatoglossus by its contraction closes 
the isthmus faucium, and shuts off all communication with the mouth. The lateral pro- 
longations of the peculiar hood-like fold, before described as existing between the root 
of the tongue and epiglottis, would seem by their contraction to engirdle the anterior 
and lateral parts of the base of the tubular prolongation of the glottis, and so fix and 
bind together the organs forming this aperture. The anterior nares or blowholes being 
now opened by the action of the muscles before described for this purpose, and the 
fibrocartilaginous pads being at the same time withdrawn from the nasal passages by 
the appropriate muscles, the contained air is expelled, and this by its expiratory 
momentum may likewise assist in freeing the channel. 
This act of blowing or spouting has been represented by G. Cuvier and others as 
having the appearance as if the animal forcibly ejected from its nostrils a large mass of 
water, and it has therefore been conjectured that the creature for this purpose must 
necessarily be furnished with some peculiar anatomical contrivance to retain such fluid. 
But this phenomenon may be accounted for in a different way, and without the gratui- 
tous assumption of the animal having any such reservoir, which, so far as the anatomical 
structure of the present specimen bears on the point, is an assumption absolutely 
groundless. 
Expiration is most probably commenced when the animal’s head is near, but as yet 
beneath the surface of the water, and when but a slight stratum of fluid is lying above 
the outer orifices of the blowholes, which as the creature expires, combined with the 
mdccclxviii. 2 M 
