3 22 NORMAL HISTOLOGY. 



since the lymphatics are provided with fairly complete endothelial walls. It 

 is probable that the lymph-paths within the papillae are closely related to the 

 intercellular clefts of the epidermis. Migratory leucocytes often find their 

 way into the cuticle where they then appear as the irregularly stellate cells of 

 Langerhans seen between the epithelial elements. A wide-meshed deep 

 plexus of lymphatics is formed within the subdermal layer, from which the 

 larger lymph-trunks pass along with the subcutaneous blood-vessels. 



The numerous nerves within the highly sensitive integument are chiefly 

 the peripheral processes of sensory neurones which terminate in free arbor- 

 izations between the epithelial elements of the cuticle, or in relation with 

 special endings located, for the most part, within the corium or subdermal 

 connective tissue. Some sympathetic fibres, however, are present to supply 

 the tracts of involuntary muscle that occur within the walls of the blood- 

 vessels or in association with the hairs and the sweat-glands. 



On entering the skin the medullated nerves traverse the subdermal 

 layer, to which they give off twigs in their ascent, and, passing into the 

 corium, within the papillary stratum divide into a number of branches. 

 Those destined for the epidermis beneath the latter break up into many 

 fibres which, losing their medullary substance, enter the cuticle and end in 

 ramifications between the epithelial cells as far as the outer limits of the 

 stratum germinativum. The ultimate endings of the fibrillae, whether taper- 

 ing or slightly knotted, always occupy the intercellular channels and are 

 never directly connected with the substance of the epithelial elements. 

 Special tactile cells (Fig. no) occur in the human epidermis, particularly 

 over the abdomen and the thighs. They are spherical or pyriform and 

 occupy the deeper layers of the cuticle ; on the side directed towards the 

 corium, they are in contact with the end-plate or meniscus of the nerve. 

 The nerve-fibres particularly concerned with the sense of touch terminate 

 within the connective tissue portion of the skin in special end-organs. 

 The structure of these end-organs is elsewhere described (pages 7983), 

 their chief locations being here noted. 



Meissner' s corpuscles (Fig. 112) are especially numerous in the tactile 

 cushions on the flexor surface of the hands and feet. While much more 

 plentiful in all the tactile pads than in the intervening areas, the touch cor- 

 puscles are most abundant in those on the volar surface of the distal 

 phalanges, where they approximate twenty to the square millimeter (Meiss- 

 ner). Their favorite situation is the apex of the papillae, where they appear 

 as elongated elliptical bodies, sometimes in pairs, whose outer pole lies imme- 

 diately below the epidermis. These corpuscles are additionally, although 

 sparingly, distributed on the dorsum of the hand, the flexor surface of the 

 forearm, the lips, the eyelids, the nipple and the external genital organs. 



The Vater-Pacinian corpuscles (Fig. 117) are well represented in the 

 hands and feet and usually occupy the subdermal tissue, although sometimes 

 found within the corium. Their distribution corresponds closely to that of 

 Meissner's corpuscles, being most generous beneath the tactile cushions. 



The Golgi- Mazzoni corpuscles are modifications of the Pacinian bodies 

 and, like the latter, are found within the subdermal tissue. 



The end-bulbs of Krause (Fig. 113) occur within the corium, either 

 slightly below or within the papillas, on the lips and external genital organs, 

 as well as probably in other regions. 



The genital corpuscles (Fig. 114) lie within the corium of the modified 

 skin covering the glans penis and the prepuce and the clitoris and surround- 

 ing parts of the nymphae. 



