THE DIGESTIVE TRACT. 591 



row. The furrow may divide the central papilla into two parts, 

 or be very shallow. The secondary papillae are present on the 

 upper surface of the central papillae only. The smooth epithelial 

 investment in the lateral portions of the papilla, and also of its 

 surrounding wall, contains peculiar bud-like formations (Schwalbe, 

 Loven) the gustatory buds. (See Fig. 250.) These are com- 

 posed, at their periphery, of large, imbricated, so-called covering 

 epithelia, while in the center of the bud delicate spindle-shaped, 

 so-called gustatory, epithelia are inclosed. Their connection with 

 non-medullated nerve-fibers has not as yet been conclusively 

 proved. The apex of the gustatory bud is marked by a shallow 

 depression. The ledges along the lateral borders of the tongue 

 are called papillae foliatce, and are composed of a number of coal- 



FlG. 250. ClKCUMVALLATE PAPILLA OF THE TONGUE OF MAN. 



E, epithelial layer ; G, gustatory bud ; C, connective tissue with injected blood-vessels ; M, 

 mucous gland with duct. Magnified 150 diameters. 



esced papillary formations of the mucosa, with interspersed 

 fungiform papilla?. In these ledges, which in man are not con- 

 stant formations, gustatory buds have also been found. 



The glandular prolongations of the epithelium, covering the 

 tongue, are simple acinous and racemose mucous glands, similar 

 to those of the mucosa of the oral cavity in general. They are 

 large in the neighborhood of the circumvallate papillae, and ramify 

 between the superficial muscle-bundles ; some of them empty in 



