THE SKIN. 569 



may be absent. The upper portion of the outer root-sheath is 

 'composed of stratified epithelia, the most external . lay er being 

 distinctly columnar. This columnar row is the last one left, as 

 the outer root-sheath approaches the region of the bulb, and, 

 gradually becoming thinner, is at length entirely lost at the 

 height of the bulb, whose formation it does not enter at all. 

 The boundary line between the outer and the inner root-sheath 

 is marked by the presence of a so-called structureless or cuticular 

 membrane. External to the outer root-sheath we find the follicle, 

 a connective-tissue formation, with interspersed circular muscle- 

 spindles, connected with those of the arrector pili muscle. Be- 

 tween the follicle and the outer root-sheath there is usually a 

 broad homogeneous layer, which can be traced around the bulb 

 of the root and the papilla of the hair. 



The papilla of the hair is composed of a delicate fibrous or 

 myxomatous connective tissue, freely supplied with plastids 

 having the appearance of spindle-shaped nuclei, and traversed 

 by a number of capillary blood-vessels. The apex of the papilla 

 in our specimen is not distinctly separated from the epithelia of 

 the hair. The line of demarcation, however, as a rule, is distin- 

 guished by the presence of a row of columnar epithelia or by the 

 medullary corpuscles. 



Outside of the follicle we find the fibrous connective tissue 

 of the derma, built up by longitudinal and transverse bundles. 

 At the bottom of the hair follicle, in the human skin, a longitu- 

 dinal tract of fibrous connective tissue is often found, which runs 

 in the direction of the hair, and carries the blood-vessels (G. 

 Wertheim). 



In comparing what I have said about the theory of the forma- 

 tion of the hair with specimens of the skin, a satisfactory con- 

 gruence will be found. This theory, as I have taught for nearly 

 seven years in my laboratory, will explain the fact that upon 

 pulling a hair the inner root-sheath is drawn out simultaneously 

 with the root. It furthermore explains the process of shedding 

 and the new formation of the hair. 



(8) The Hair. As before mentioned, the part of the hair im- 

 planted in the skin is called the root, while the portion projecting 

 above the surface of the skin bears the name of shaft. Its main 

 mass is composed of delicate, flat, nucleated, fusiform epidermal 

 scales, which are firmly attached to each other, but may be 

 isolated by soaking in dilute acetic acid. The darker the com- 

 plexion of the individual, the greater is the amount of granular 





