240 
DRS. A. CARTE AND A. MACALISTER ON THE 
On dissecting off the muscles, a large solid central cartilaginous crest or primordial 
vomer was disclosed which extended anteriorly from the point of the snout, where it 
passed 7 inches in advance of the bony vomer and completed the median portion of the 
roof of the mouth, to the divergence of the intermaxillary bones posteriorly, where it 
divided into three ; the two lateral parts passed forwards and gave support to the con- 
strictor naris; the central division anteriorly, where it joined the primordial vomer, was 
cartilaginous, but posteriorly and superiorly it became fibrous. 
The external or alar fibrocartilages were oval in shape, and so arranged as to be 
capable of completely stopping the nasal apertures ; they were composed of a soft fibro- 
cartilage permeated, especially on the external side, with fat-cells, which rendered them 
highly elastic ; their inner or nasal surface was lined with a thick mucous membrane, 
arranged in longitudinal folds and of a deep bluish-black colour ; on raising this a strong 
muscle was exposed, which arose from the outer side of the median cartilaginous crest, 
from whence it ran backwards and was inserted into the outer side of the nasal fibro- 
cartilage ; this muscle by its contraction would draw forwards and inwards the anterior 
extremity of the fibrocartilage, and so remove it from the nasal aperture, leaving this 
orifice perfectly free. The closing of these orifices appeared to depend, in a great mea- 
sure, on the relaxation of this muscle. 
On raising the posterior border of the second plane of muscles, a large nerve, the infra- 
orbital branch of the fifth pair, was seen emerging from the foramen in the superior 
maxilla ; it divided into three branches, which were traceable into the muscles and inte- 
guments of the nares. 
As the blowholes are the only orifices through which the atmospheric air is allowed 
to pass during the act of respiration, we find accordingly that these outlets are amply 
provided with the means of carrying on this important function. Their alee can be 
divaricated by the simultaneous action of the superficial and deep muscular planes, and, 
on the other hand, they could be brought together by the middle plane of fibres, which 
from their fasiculi running in an elliptical direction on each side of the blowholes, 
formed a regular sphincter and approximate the external lips of the orifices ; at the same 
time the central portion of the muscle, from its deep-seated position, would press the ex- 
ternal or alar cartilages against the septum, and so completely close these passages; the 
pressure of water from the outside may account for the fact that the muscles for opening 
are much more powerful than those for closing these canals. 
There are some points worthy of notice respecting the mechanism by which the func- 
tions of respiration and deglutition are performed, in this and other Cetaceans, which we 
think have not hitherto been clearly explained. 
As regards the first or respiratory function, it is obvious that when the animal ap- 
proaches the surface of the ocean its first act will necessarily be that of expiration, in 
order to expel from its lungs the deoxidized air contained therein after the preceding 
inspiratory act ; expiration is accomplished in a great measure, as in other mammals, 
by the contraction of the abdominal muscles drawing in the ribs, and propelling upwards 
