684 



Define 

 septum, 



hyo-glossal 

 membrane, 



and inferior 

 lingualis. 



Fibrous 

 structures 

 of tongue. 



Septum. 



Hyo-glossal 

 membrane. 



Submucous 

 layer. 



Muscles in 

 each half : 



two kinds. 



Extrinsic : 

 number. 



Dissection 

 of palato-, 

 stylo-, and 

 hyo-glossus 



DISSECTION OF THE TONGUE. 



the lingual vessels and nerves. The tongue is enveloped by mucous 

 membrane ; and a special fibrous layer attaches it to the hyoid bom 



Dissection. To define the septum, and the membrane attaching 

 the tongue to the hyoid bone, the tongue is to be placed on its 

 dorsum ; and, the remains of the right inylo- and genio-hyoid 

 muscles having been removed, the genio-glossi muscles are to be 

 cleaned, and drawn from one another along the middle line. After 

 separating those muscles, and cutting across their intercommuni- 

 cating fibres, the edge of the septum will appear. By tracing the 

 hinder fibres of the genio-glossus muscle towards the hyoid bone, 

 the hyo-glossal membrane will be arrived at. 



On the outer side of the genio-glossus muscle is the longitudinal 

 bundle of the inferior lingualis, which will be better seen sul 

 quently. 



Fibrous tissue. Along the middle line of the tongue is placed a 

 thin lamina of this tissue, forming a septum ; the root of the tongue 

 is attached by another fibrous structure, the hyo-glossal membrane ; 

 and covering the greater part of the organ is a submucous layer of 

 the same tissue. 



Septum. This structure forms a vertical partition between the two 

 halves of the tongue (fig. 243, B, p. 686), and extends from the base 

 to the apex, but does not reach to the dorsum. It is thicker behind 

 than in front, and is connected posteriorly with the hyo-glossal 

 membrane. To each side the transverse muscle is attached. Its 

 disposition may be better seen subsequently on a vertical section. 



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-glossi are inserted, as if this was their 

 aponeurosis to attach them to the hyoid bone. 



The submucous fibrous stratum of the tongue invests the organ, and 

 is continued into the sheaths of the muscles. Over the posterior 

 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 

 intrinsic 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 organ that 

 is to say, springing from one part and ending at another. 



The extrinsic muscles (fig. 242) are the following : palato-glossus, 

 stylo-glossus, genio-glossus, hyo-glossus, chondro-glossus, and pharyn- 

 geo-glossus. Only the lingual endings of these, except in the case 

 of the chondro-glossus, are now to be studied. 



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 ; and, to follow their radiating 



