558 DE. J. MUEIE ON THE ANATOMY OF THE SEA-LION. 



form the floor of the cavity (these have been described along with the organs of voice) ; 

 but on either side of them are several longitudinal elastic folds of membrane (aryteno- 

 epiglottidean folds) connecting the root of the epiglottis with the wavy plications of 

 the oesophageal portion of the pharynx. 



Inferior constrictor. — Under this head I shall describe what represents the above in 

 human anatomy ; but here it may conveniently be subdivided into two portions, although 

 the fibres of these in the median line closely intermingle with one another. 1. The 

 crico-pharyngeal portion springs as a narrow strong muscular band from the posterior 

 hinder (inferior) angle of the cricoid cartilage, close to and somewhat overlapping the 

 margin of the crico-thyroid muscle. Its fibres curve slightly forwards and round the 

 oesophagus, mingling, as already hinted, with the second portion. 2. The thyro- 

 pharyngeal portion is much the broader, and consequently stronger, of the two. Its 

 origin is from the surface of the thyroid cartilage between its oblique line and upper 

 posterior oesophageal border ; whence the fibres are directed in an arched manner, 

 meeting their fellows from the opposite side, and with scarcely any median fibrous 

 raphe. The anterior median fibres curve in an angular manner forwards, considerably 

 overlapping those of the middle constrictor. 



Middle constrictor. — Like the last, this is an expanded, tolerably thick, fleshy 

 layer, the fibres of which are coarse and present clefts such as might suggest separa- 

 tion of portions, as in the preceding ; moreover its points of attachment are more 

 numerous than in that muscle. Its most posterior origin is a superficial slip which 

 overlaps the thyro-hyoid muscle. Fibres joining this slip come deeply from the thyro- 

 hyoid ligament immediately adjoining the superior laryngeal nerve ; this portion arches 

 towards the middle line. The broader portion in advance of this arises from the thyro- 

 idal nearly its whole length. This attachment has fibres in conjunction with the 

 thyro-hyoid muscle which it overlaps ; in the same way it overrides and commingles 

 with the origin of the hyoglossus, and in turn itself is overlapped by the outwardly 

 expanded posterior fibres of the genio-hyoid, which, indeed, intimately mix with it. 

 On the right side a further narrow slip arose from the thyrohyal. From these several 

 sources the fibres proceed round to meet their fellows of the opposite side. Posteriorly 

 they are arched considerably, so that part of the muscle passes under the inferior 

 constrictor, the hinder border being convex. About the middle they are nearly 

 transverse, and in front present a concavity forwards, the centre being attached to 

 the skull. 



The superior constrictor underlies the fore part of the latter muscle, and is altogether 

 very much weaker. 



3. Alimentary Canal. 



a. Relative positions of the Abdominal Viscera. — A longitudinal median incision having 

 been made into the abdomen from the ensiform cartilage to the pubis, the contained 

 viscera were found disposed in the undernoted condition. The Liver, which occupies 



