STRUCTURE OF THE TOXGUE. 147 



posterior third of the tongue : their number varies from eight to ten 

 These papillae extend across the tongue in a line resembling the letter V 

 with the point turned backwards. Each papilla consists of a central 

 truncated part of a conical form, which is surrounded by a fold of the 

 mucous membrane ; its wider part or base projects above the surface, 

 whilst the apex is attached to the tongue. Both the papilla and the sur- 

 rounding fold are furnished with smaller secondary papillae. 



Minute simple papillae exist behind the calciform kind, and on the under 

 surface of the free portion of the tongue ; but they are not observed till 

 the epithelium is removed. 



Taste buds. Around the circumvallate papilla; is a circle of small 

 peculiar bodies, which are covered by the epithelium : they are like a 

 small carafe in shape, the base resting on the corium. They are formed 

 of elongated epithelium-like cells, of which the central, resembling olfac- 

 torial cells, are supposed to be connected with the nerve of taste. 



A small collection of similar bodies occupies the back of the tongue, on 

 each side, just in front of the anterior pillar of the fauces. 



Structure of the Papillae. The simple papillae are constructed like 

 those of the skin, viz. of a projecting cone of membrane, which is covered 

 by epithelium, and filled with a loop of capillaries, and a nerve. 



The other compound forms of the papillae may be said to be produced 

 by outgrowths from the simple kind. Thus smaller papillary eminences 

 spring from the common cone of limiting membrane ; and each has its 

 separate investment of epithelium, by which the brush-like appearance on 

 the surface is produced. From the plexus of capillary vessels in the in- 

 terior of the papilla a looped offset is furnished to each smaller papillary 

 projection. The entering nerve sends offsets to the different subdivisions 

 of the papilla, on some of which end-bulbs may be recognized. 



STRUCTURE. The tongue consists of two symmetrical halves separated 

 by a fibrous layer in the middle line. Each half is made up of muscular 

 fibres with interspersed fat ; and entering it are the lingual vessels and 

 nerves. The whole tongue is enveloped by the mucous membrane ; and a 

 special fibrous membrane attaches it to the hyoid bone. 



Dissection. To define the septum, and the membrane attaching the 

 tongue to the hyoid bone, the tongue is to be placed on its clorsum ; and, 

 the remains of the right mylo- and genio-hyoideus having been removed, 

 the genio-hyo-glossi muscles are to be cleaned, and drawn from one another 

 along the middle line. After separating those muscles, except for an inch 

 in front, and cutting across their intercommunicating fibres, the edge of 

 the septum will appear. By tracing the hinder fibres of the genio-hyo- 

 glossus muscle towards the os hyoides, the hyo-glossal membrane will be 

 arrived at. 



Outside this triangular muscle in the middle line, is the longitudinal 

 bundle of the inferior lingualis, which will be better seen subsequently. 



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

 lamina of this tissue, forming a septum : its root 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. 37, H ), and extends from the base to the apex. 

 It is thicker posteriorly than anteriorly, and is connected behind with the 

 hyo-glossal membrane. To each side the transverse muscle is connected. 

 Its disposition may be better seen subsequently on a vertical section. In 



