THE SKIN. 359 



masses, situated just beneatli the cutis, in almost every part of the sur- 

 face of the body. Each is formed by the convolution of a single tube, 

 which thence runs towards the surface, as the efferent duct, making 

 numerous spiral turns in its passage through the skin, and penetrat- 

 ing the epidermis rather obliquely ; so that its orifice is covered by a 



1 



f.1-71. 



No. 1. Distribution of the tactile nerves at the extremity of the fingers, as seen in a 

 thin perpendicular section of the skin. No. 2. Termination of loops of nerve- in 

 the muscles. 



sort of little valve of scarf-skin, which is lifted up as the fluid issues 

 from it. Mr. Erasmus Wilson says : " To arrive at something like an 

 estimate of the value of the perspiratory system, in relation to the rest 

 of the organism, I counted the perspiratory pores on the palm of the 

 hand, and found 3528 in a square inch. Now, each of these pores 

 being the aperture of a little tube of about a quarter of an inch long, it 

 follows that in a square inch of skin on the palm of the hand there 

 exists a length of tube equal to 882 inches, or 73i feet. Surely such 

 an amount of drainage as 73 feet in every square inch of skin assum- 

 ing this to be the average for the whole body is something wonderful ; 

 and the thought naturally intrudes itself, What if this drainage were 

 obstructed ?"* Could we furnish a stronger illustration, of the neces- 

 sity for maintaining the skin in a healthy state 1 



The oil-glands of the skin are similar in structure to the perspira- 

 tory ducts, being composed of three layers derived respectively from 

 the scarf-skin, which lines their interior ; the sensitive skin, which is 

 the medium of distribution for the vessels and nerves ; and the corium, 

 with its fibres, giving them strength and support. Like the per- 

 spiratory tubes, they are in some situations spiral ; but this is not a 

 constant feature ; more frequently they pass directly to their destina- 

 tion they are also larger, as shown in the drawing, proceeding from 

 the oil or fat vesicle situated at its lower extremity. Oil-glands are 

 freely distributed to some parts, whilst in others they are entirely 



* Wilson on the Management of the Skin. 



