1132 



TONGUE. 



the subject that have been made, namely those 

 of Mr. Bowman, as published in the " Philo- 

 sophical Transactions," and in the " Physio- 

 logical Anatomy " of himself and Dr. Todd, I 

 would advance them with diffidence, and some- 

 thing like hesitation. The appearances that I 

 have invariably seen, by daily examinations for 

 some time, of sections from many tongues, is 

 this: each fibre, before its termination, gradu- 

 ally tapers, in a fusiform manner, with more or 

 less of acuteness ; sometimes the tapering is 

 rather sudden, in other cases very much pro- 

 longed (Jig. 752. A) ; in all the tapering is con- 



Fig. 752. 



A. Fasciculus of the vertical fibres of the tongue, 

 showing their fusiform extremities and the ter- 

 mination of each muscular fibre in a filament of 

 white fibrous tissue. (Magnified 100 diameters. 

 B. Magnified 200 diameters). 



tinned so far that the muscular tissue becomes 

 nearly as fine as the fibrous tissue in which it 

 terminates : from this fine extremity the fibre 

 passes off, and the appearances at the point of 

 transition are of two sorts ; the one as seen 

 at B, a, where the muscle passes smoothly 

 off in the fibrous tissue, and you cannot tell 

 where the one commences and the other ends ; 

 the other as seen at B, b , where the pointed 

 extremity of the muscle is a little rounded, 

 and its outline plainly visible ; but in this case, 

 also, the diameter of the extremity of the 

 muscle as nearly as possible coincides with 

 that of the fibre. It is possible that the dif- 

 ference of appearance may depend in some 

 degree upon difference of focus, but, certainly, 

 I have not been able, in some cases, by any 

 adjustment of focus, to get a clear definition of 

 the point where the muscular structure termi- 

 nated. In those cases where the outline of 

 the termination of the muscle is defined, the 

 transverse striation may be traced up to its 

 very extremity ; where the outline of the one 

 merges in that of the other, the striae seem also 

 gradually to be lost, becoming a linear series 

 of little dots, and so fading away (B, a). 



The conclusion that the appearance at once 

 suggested to me was, that the sarcolemma, 

 condensed by the diminution of its contents, 

 passed off from the acuminated extremity 

 as a tendon of white fibrous tissue ; and 

 this opinion was confirmed when I thought 

 of the genesis of these structures. If, as 

 seems probable from the account given by 

 Schwann and other physiologists of the de- 

 velopment of muscle, the sarcolemma is 

 the persistent cell-wall of the original for- 

 mation-cells of the fibre, and if white fibrous 

 tissue is true zellenfasern altered cell-wall 

 of cells that have become elongated at their 

 opposite nodes, and plicated as it were, 

 then we reduce the sarcolemma and the 

 white fibrous tissue to the same category 

 altered cell-wall. The function of the cell- 

 wall of the muscle-cell is to secrete that 

 peculiar matter within it which ultimately 

 becomes sarcous matter ; the function of the 

 cell-wall of the fibre-cell is to become elon- 

 gated and plicated, or otherwise longitudinally 

 striated. To explain, therefore, the gradual 

 passage of one structure into the other, we 

 have merely to suppose, on the part of the cell- 

 wall, the gradual mergence of one function, 

 and taking on of the other. These considera- 

 tions at any rate tend to obviate any ante- 

 cedent objections to the opinions suggested by 

 the appearances, that would have arisen if 

 there had been any thing essentially heteroge- 

 neous in the nature of the structures con- 

 cerned. The fact, that Mr. Bowman's obser- 

 vations were made on the lower animals 

 fish, Crustacea, and insects may perhaps 

 account for the difference of the appearances. 

 It is a subject that requires more investiga- 

 tion, and no structures seem to me so much 

 adapted for this purpose as the tongues of the 

 lower vertebrata. 



b. Extrinsic muscles of the tongue. These 

 are four in number, the pulatoglossus, the stylo- 

 g/ossits, the hyoglossus, and the genioglossus ; at- 

 taching the tongue to the soft palate, base of 

 the skull, hyoid bone, and lower jaw, and mov- 

 ing it nearly in the four cardinal directions, up- 

 wards, downwards, backwards, and forwards. 

 They are all more or less of a mixed nature, 

 being continued in some degree into the 

 tongue. They move the organ en masse, and 

 attach it to distant parts by virtue of their 

 extrinsic portion ; they contribute to the sub- 

 stance of the organ, and affect its form, by 

 virtue of their intrinsic portion. It is this 

 continuity of the substance of the tongue with 

 its means of connection to distant parts that 

 makes those connections so strong and safe; 

 it is this prolongation of the extrinsic muscles 

 into the tongue that renders the association 

 of the extrinsic and intrinsic movements so 

 intimate. 



The palatoglossus (glosso-stap/>y/hu/s) t the 

 smallest of these muscles, constitutes the 

 connection between the soft palate and the 

 sides of the tongue. At its origin in the soft 

 palate its fibres are mingled witli those of 

 the palatopharyngeus ; as it descends to the 

 tongue it becomes much narrower, constitut- 



