:;;{'-, THE DIGESTIVE M'I'AHATUS IN MAMMALIA. 



parably thinner and loss donso on tho sides of the fixed portion and the 

 inferior plane of tho free part ; on tho dorsnm of tho tongue it is difficult to 

 cut it. Its deep face receives tho insertion of a large numl>cr of the muscular 

 fibres of the organ, and for the greater part of its extent it adheres in tho 

 most iutimato manner to these fibres ; though its adherence is not so closo 

 at those points where it is in contact with the labial glandules. 



Its superficial face is not smooth, but shows a prodigious quantity of 

 minute prolongations or papillae, which, according to their shape, arc dis- 

 tinguished VLB filiform, fungiform, and calyciform papillcK. 



The filiform papillce are formed by thin prolongations terminating in a 

 point, each being covered by an epithelial sheath which greatly increases its 

 dimensions. They are simple or composite, having at their summit 

 secondary prolongations, much smaller, and provided also with an epithelial 

 covering. These filiform papilla are largest on tho middle part of the 

 dorsum of tho tongue, where they present a tufty appearance ; towards the 

 point of the organ they are imbedded in epithelium, and are scarcely 

 apparent in tho minute elevations on its surface. 



The fungiform papillce (p. capitatce) are club or sponge-shaped elevations 

 of the dorm, attached to the membrane by a short pedicle. Their surface is 

 convex and smooth, or studded with filiform papilla). They are scattered 

 irregularly over the dorsum of tho tongue, among tho filiform papilla), and 

 are most numerous on tho posterior third of its surface. 



The calyciform papillce (fossulate, circumvallate, or lenticular papillae) are 

 really fungiform, but instead of projecting above the free surface of the dorm, 

 they are placed in a depression of this membrane. They are surrounded 

 by a slightly-elevated ring, within which is a narrow fossa around the 

 pedicle of tho papilla ; several papilla) may bo contained within one cup- 

 shaped cavity. They only exist at the base of the tongue, where two of 

 their number, very developed and composite, correspond to the blind Jioles of 

 Morgagni (foramen caecum). At tho base of a certain number of the fungi- 

 form and calyciform papillte is a band of adenoid tissue. 



It is generally believed that these three kinds of papillae have each a 

 distinct function ; the filiform are to retain the alimentary and sapid sub- 

 stances on tho surface of the tongue ; the fungiform are tactile organs, and 

 the calyciform are gustatory. 



2. Muscles. Beneath the mucous membrane, on the dorsal surface of 

 the tongue, is a cylindrical fibrous cord which sometimes attains tho thick- 

 ness of a largo goose-quill. This cord is situated in the median plane, 

 near the middle part of the organ, and is from 2 to 3 inches long. It may 

 bo considered as a fibrous support to the muscular tissue, and it sometimes 

 directly adheres to tho deep surface of the tegument. At other times, it is 

 only connected with that membrane by a very short lamellar prolonga- 

 tion, and is then buried a little deeper among tho fibres of tho superior 

 muscular layer. 



(The German hippotomists designate this tho cartilage of the tongue. It 

 is only found in Solipeds, and was first described by Briihl, who gave it this 

 designation. Loyh states that it is composed of dense fibro-cartilago, 

 surrounded by cellular and adipose tissue ; that it is from 4 to 7 inches 

 long, and ths to 1 inch in thickness ; and that it commences about an inch 

 from tho anterior appendix of tho hyoid bone.) 



A similar cord, but not so strong or well defined, is sometimes found at 

 tho inferior surface of tho free portion of the tongue. 



Intrinsic muscles. In studying the proper substance of the tongue in 



