176 SPECIAL HISTOLOGY. 



cells ; in other words, to be the boundary lines of the separate elements 

 of the cortex, and sometimes I consider them to be their nuclei. For, 

 even in the shaft of the hair, the cortical plates all contain fusiform 

 nuclei 0-01-0-016 of a line long, 0-0005-0-0012 of a line broad, which 

 may, in fact, be isolated by rubbing down white hairs which have been 

 boiled in caustic soda. Besides these, there appear in the cortical sub- 

 stance, and with especial distinctness in a whitish place immediately 

 above the bulb, certain fine striae, which are produced by inequalities in 

 the surface of the cortical plates, and which do not readily disappear, 

 even after the continued action of alkalies, but eventually give place to 

 a finely fibrous appearance ; they cannot be isolated, but are visible in 

 those portions of the cortex which have been separated by sulphuric 

 acid, and sometimes even are very distinct (Fig. 66). 



The description of the cortex, which has just been given, holds good 

 especially for the hair-shaft. In the root of the hair, so long as it is still 

 solid and brittle, we find essentially the same conditions ; and it is only 

 in its lower half, where it becomes gradually softer, at first finely fibrous 

 and then granular, that the structure of the cortex undergoes a progres- 

 sive change. Here, in fact, the above described plates .are less rigid, 

 and take on more and more distinctly the form of elongated cells (Fig. 

 66) of 0-020-0-024 of a line in length, and 0-009-0-011 of a line in 

 breadth, whose cylindrical, straight, or serpentine nuclei of 0-008-0-01 

 of a line, are very easily rendered visible by the action of acetic acid, and 

 may also be readily isolated. The soft and shortened plates then pass 

 pio> fifi into elongated, rounded cells, with short nuclei, the 

 fibrous structure becoming more and more obliterated, 

 and these are finally continued without interruption into 

 the elements of the lowest and thickest part of the hair, 

 the bulb. They (Fig. 67) are nothing more than round 

 cells of 0-003-0-006 of a line, which lie closely pressed 

 together ; and like the cells of the mucous layer of the epidermis 

 sometimes contain only colorless granules, sometimes are so 

 full of dark pigment-granules, that they become true pigment- 

 cells. It must be added, that the chemical relations of the 

 cortex are altered in the lower half of the root, its elements becoming 

 more sensitive to the action of acetic acid, which does not affect the 

 plates of the shaft at all ; they swell up and dissolve in alkalies also, 

 much more quickly than those of the shaft.* 



FiG. 66. Two cells from the cortex of the root of the hair (the finely-striated part of it 

 immediately above the root), with distinct nuclei and a striated appearance; magnified 

 350 diameters. 



FiG. 67. Cells from the deepest part of the bulb of the hair; magnified 350 diameters: 

 a, from a colored bulb, with pigment-granules and somewhat hidden nucleus; b, from a 

 white hair with a distinct nucleus and few granules. 



*[Reichert ("Bericht"' for 1850, Mull. " Archiv," 1851) asserts that the cortical substance 



