604 MANUAL OF HISTOLOGY. 



siderable variety among themselves as to position, size, and shape (fig. 

 565). In certain localities as, for instance, in the palmar aspect of 

 the hand they are frequently aggregated in small groups arranged along 

 the ridges of the corium. 



At other spots the grouping is more irregular, and the papillae are some- 

 times found widely scattered, at others crowded together. Their size also 

 varies greatly. The longest, rising to 0-1505, or even 0'23 mm., are to 

 be found on the volar aspect of the hand, the sole of the foot, and nipple. 

 The most usual length of the papillae is 0'1128-0'0564: mm. ; but small 

 examples, such as those found, for instance, ill the face, may not measure 

 more than '045 1-0 '037 7, or even less. The largest of them are conical or 

 tongue-shaped, but the smaller are truncated, or merely slight elevations. 

 Besides the simpler papillae, there exist also compound, that is, broader 

 excrescences, running into two or more, rarely three, points (fig. 566 in 



Fig. 566. Three groups of tactile papillae from the skin of the human index finger, in 

 vertical section. Some are supplied with vascular loops, some with tactile corpuscles. 



the middle). We have before spoken of their apparently homogeneous 

 substratum, 136. Their surface, further, is thrown into ridges and 

 furrows, giving to the whole a toothed appearance (Meissner). 



"We have already said as much as necessary in regard to the muscular 

 elements of the skin 163. Bands of these pass, as we have learned 

 recently from J. Neumann, from the upper part of the cutis into the 

 panniculus adiposus, dividing frequently in their course, and sending off 

 both vertical and horizontal bundles. There occur, besides, both above 

 and below the perspiratory glands, horizontal muscular branches, especi- 

 ally in the hairy part of the scalp : these probably belong to the arrectores 

 pili ( 212). Finally, beneath the tactile corpuscles, especially those of 

 the scalp, and on the extensor aspect of the limbs, are to be found other 

 sets of bands of unstriped muscle. In different individuals, however, 

 considerable variety exists in this respect. 



The vascular network of the skin commences in the subcutaneous 

 areolar tissue in the form of round meshes enclosing the fat cells, and 

 capillary interlacements around the hair follicles and convoluted ends of 

 the perspiratory ducts (fig. 567, c). In the corium itself, we encounter a 

 very complicated plexus of fine capillary tubes, 0'0074 to 0'113 mm. in 

 diameter. These spread out horizontally, and supply the greater part of 

 the papillae with loops on an average 0'0090 mm., except at those points 

 where some of the papillae contain tactile corpuscles, in which case they 

 are without vessels ( 1.85). 



The lymphatics of the skin, known to earlier observers as very dense 

 networks, have recently been closely studied by Teichmann, and more so 

 still by Neumann. 



In the corium these present a system of tubes possessing independent 

 walls, and arranged in two different dense networks, a deeper, of coarser 

 canals with wider meshes ; and a more superficial, of finer passages with 



