436 



INNERVATION. 



[CHAP. xv. 



Fi - 94 - In their compound nature they 



present much resemblance to the 

 intestinal villi of the rhinoceros 

 and other large animals. We have 

 further ascertained the existence 

 of similar minute papillae, inter- 

 spersed very unequally among the 

 compound forms, as well as occu- 

 pying much of the surface behind 

 the circumvallate variety, where 

 the compound forms do not exist. 

 These minute papillae seem to 

 have hitherto escaped detection, in 

 consequence of their being com- 

 pletely buried and concealed under 

 the common sheet of epithelium. 



If we examine the mucous mem- 

 brane immediately in front of the 

 epiglottis, we find it perfectly 

 smooth, almost transparent, and 

 supplied by capillary vessels spread 

 uniformly under the surface, and 



connected with simple plain sub- 

 Tongue seen on its upper surface : a. One of 



the circumvallate papillae, b. One of the fungiform niUCOUS pleXUSCS Ol arteries and 

 papillae. Numbers of the conical papillae are seen , .,, 



about d, and elsewhere, e. Glottis, epiglottis, and VCIUS I here the papillary tlSSUC IS 

 glosso-epiglottidean folds of mucous membrane. n -. -, -^ ., /> 



From scemmering. undeveloped. Further forwards, 



however, where the membrane, still seems smooth, the plexus of 

 arteries beneath it sends upwards, at pretty regular intervals, a series 

 of twigs, each of which terminates in one or two capillary loops, 

 sometimes dilated in the bend, from which a small vein returns the 

 blood to the submucous venous plexus. These loops correspond to 

 those of the simple papillae of the skin, p. 411; they supply simple 

 papillae, buried under a common investment of scaly epithelium, 

 that differs from the cuticle only in its greater tenuity and moist- 

 ness. On the removal of this delicate epithelium by maceration, the 

 papillae stand out free from the membrane, and are seen to consist 

 of an envelop of basement membrane (p. 404), enclosing a paren- 

 chyma obscurely granular, with the capillary loop already mentioned. 

 After much care, we have not been able to see nervous tubules within 

 them; but they must exist under some important modification, whicl 

 most probably consists in the absence of their characteristic white sub- 

 stance of Schwann. These simple papillae are represented in fig. 95. 



