148 DISSECTION OF THE TONGUE. 



sonic instances a small fibro-cartilage, about a quarter of an inch deep and 

 lonr, exists in the septum. 



The hyo-glossal membrane is a thin but strong fibrous lamina, which 

 attaches the root of the tongue to the upper border of the body of the 

 hyoid bone. On its under or anterior surface some of the hinder fibres of 

 the genio-hyo-glossi are inserted, as if this was their aponeuroses to attach 

 them to the os hyoides. 



The submucous fibrous or aponeurotic stratum of the tongue invests the 

 organ, and is continued into the sheaths of the muscles. Over the pos- 

 terior third of the dorsum its strength is greater than elsewhere; and in 

 front of the epiglottis it forms bands in the folds of the mucous membrane 

 in that situation. Into it are inserted the muscular fibres which end on 

 the surface of the tongue. 



MUSCLES. Each half of the tongue is made up of extrinsic and in- 

 trinsic muscles. The former or external are distinguished by having only 

 their termination in the tongue ; and the latter or internal, by having both 

 origin and insertion within the origin that is to say, springing from one 

 part and ending in another. 



The extrinsic muscles (fig. 37) are the following : palato and stylo- 

 glossus, hyo and genio-hyo-glossus, and pharyngeo-glossus. Only the 

 lingual endings of these are now to be looked to. 



Dissection. After the tongue has been firmly fastened on its left side, 

 the extrinsic muscles may be dissected on the right half. Three of these 

 muscles, viz., palato-, D, stylo-, B, and hyo-glossus, c, come together to the 

 side of the tongue, at the junction of the middle and posterior third ; and, to 

 follow their radiating fibres forwards, it will be necessary to remove from 

 the dorsum, between them and the tip, a thin layer consisting of the mu- 

 cous membrane and fleshy fibres of the upper lingualis. Beneath the tip 

 a junction between the stylo-glossus muscles of opposite sides is to be 

 traced. 



The part of the constrictor muscle, o, which is attached to the tongue, 

 and the ending of the genio-hyo-glossus, will come into view on the divi- 

 sion of the hyo-glossus. 



Only the two parts of the hyo-glossus (basio- and cerato-glossus, p. 99), 

 which arise from the body and great wing of the hyoid bone, are referred 

 to above. To lay bare the third part, or the chondro-glossus, F, which is 

 a small muscular slip attached to the small cornu of the os hyoides, turn 

 upwards the dorsum of the tongue, and feel for the small cornu of the 

 hyoid bone through the mucous membrane. Then remove the mucous 

 membrane in front of the cornu, and the fibres of the muscle radiating 

 forwards will be exposed. 



The palato and stylo-glossus muscles, D and H, are partly combined at 

 their attachment to the lateral part of the tongue, and form, together with 

 the following muscle, an expansion over the anterior two-thirds of the 

 dorsum beneath the superficial lingualis. In this stratum the fibres radi- 

 ate from the point of contact of the muscles with the tongue some passing 

 almost horixon tally inwards to the middle, and others obliquely forwards 

 to the tip of the organ. 



A' great portion of the stylo-glossus is directed along the side of the 

 tongue ; and some fibres are inclined to the under surface in front of the 

 hyo-glossus, to join those of the opposite muscle beneath the tip. 



flyo-yfassus. The two superficial parts of the muscle (basio and cerato- 



