MOUTH OF MAMMALS. 389 



bone, immediately in advance of which, nineteen inches from the 

 aperture of the mouth, are situated the tonsils, each tonsil being 

 an oval patch of a thin layer of muco-glandular substance with 

 a finely reticulate surface. Behind the tonsils, and between them 

 and the basi-hyal, a pouch of the gular membrane, fig. 9, s, descends 

 between the epi-hyals ; it is one inch and a half in depth, by one 

 inch in width. The posterior margin of the soft palate terminates 

 by a low angular projection, like the rudiment of a uvula, opposite 

 the base of the epiglottis. From the sides of this uvula the mem- 

 brane arches backward, and gradually subsides upon the beginning 

 of the oesophagus. The whole length of the nasal passages is 

 twenty-two inches in the full-grown Myr.juhata. The first inch is 

 surrounded by the cartilaginous part of the nose : the next thirteen 

 inches is inclosed by bone : the last eight inches of the canal has 

 musculo-membranous walls, and is an enormously developed homo- 

 logue of the ( palatum molle ' in Man. The canal of the posterior 

 nares is continued far back beyond the base of the skull, and the 

 homologues of the ' constrictor pharyngis' act upon this canal before 

 they embrace the proper pharynx. They consist of several distinct 

 muscles. The most anterior one (cerato-pharyngeus) comes off from 

 an extent of more than an inch of the middle part of the cerato-hyal. 

 It is a thin, broad layer, the fasciculi of which diverge to spread 

 upon the sides of the postcranial continuation of the nasal passage, 

 interlacing with the constrictor fibres which spread over the back 

 part of that passage. The second muscle (epi-pharyngeus) has a 

 thicker origin, of ten lines in extent, from the back part of the 

 inner end of the cerato-hyal, and from the joint between this and 

 the epi-hyal. The fasciculi diverge and spread over the sides of 

 the posterior part of the soft nasal canal, partly overlapping the 

 preceding muscle anteriorly, and being themselves slightly over- 

 lapped by the next portion behind. The third constrictor (hyo- 

 pharyngeus) has an origin three lines in extent from the thyro-hyal 

 and contiguous part of the basi-hyal : the fibres diverge upon the 

 sides of the end of the nasal canal and the beginning of the 

 pharynx, the anterior fibres overlapping and then blending with 

 the posterior fibres of the preceding muscle. The fourth con- 

 strictor (thyro-pharyngeus) comes off from the outer margin of the 

 thyroid cartilage, having an origin of nine lines in extent. The 

 fibres pass transversely round the pharynx, partially overlapping 

 the preceding muscle, and slightly expanding at the back of the 

 pharynx. The posterior continuation of this portion, which 

 might be regarded as a fifth muscle (crico-pharyngeus), arises from 

 the posterior and outer prolongation of the cricoid, behind the 



