THE SKIN. 



369 



c. Growths of the Epidermis. Besides this desquamative 

 vegetation, the epidermis is also the seat of special growths 

 whose purpose it is to produce more or less permanent organs, 

 such as hair, nails, feathers and other corneous products. 

 The formation of the hair is the type of all the rest : the be- 

 ginning of this growth is an off-shoot of the epidermis of the 

 rete malpighianum, which sinks into the dermis, and here 

 forms a kind of sac, like the finger of a glove, more or less 

 resembling a bottle in shape (pilous follicle) ; at the bottom 

 of this cul-de-sac, which grows downwards, a shoot (Fig. 95) 

 of the epidermis is formed, which now growing upwards, 

 towards the surface, lengthens grad- 

 ually, passes along the follicle (root 

 of the hair), and, coming out, forms 

 a more or less decided protuberance 

 outside (stem of the hair: hair, 

 down). These growths are all com- 

 posed of globular elements similar 

 to those of the corneous layer, being, 

 like this, extremely hygroscopic; 

 this hygroscopy is considerably di- 

 minished by means of the fatty 

 matter which the sebaceous glands 

 spread over the skin, and with 

 which they cover the hair as soon 

 as it is developed, these glands, as 

 we shall see, opening into the upper 



part of the pilous follicles. Some 



kinds of hair (as the tactile hair of 

 the muzzle of the dog and cat) exhibit on the inside a dermic 

 papilla, which rises to a certain point in the medulla or pith. 

 This papilla is extremely vascular : it therefore would appear 

 probable that it also contains nervous elements constituting 

 it an organ of touch, which has been proved to be the case 

 (J. Dietl, by his experiments on the hair of an ox). 1 





air and of sebaceous 



1'Etude de quelques 

 "Journal de PAna- 



1 See M. Duval, " Note pour servir & 

 Papilles vasculaires" (papilles des poils). 

 tomie." 1873. 



J. Dietl, " Untersuchungen iiber Tasthaare." (In " Sitzungs- 

 berichte der Akademie der Wissenschaften." Wien., 1872, p. 62.) 



* A, "Bottom of the follicle in which is formed the hair-knob (bulbe pileux). 

 B, B, Lateral pouches, origins of the two sebaceous glands. C, Extremity of the 

 young hair, just emerging from its follicle. 1, Malpighi's layer. 2, Middle 

 layer of the epidermis. 3, Corneous layer of the epidermis. 



24 



