SECT. 65.] HAIRS. I 19 



as they were previously, the inner ones begin to develop pigment 

 in their interior and to lengthen ; being marked off at the same 

 time from the former as a conical-shaped mass, with its apex di- 

 rected upwards. At first, this central mass is perfectly soft, and, 

 like the layers of cells which surround it externally, easily soluble 

 iu soda. At a later period, however, after it, as well as the in- 

 cluding process, has grown somewhat in length, its elements 

 become harder, and separate into two portions, an inner dark pig- 

 mented, and an outer bright portion, which are, in fact, a young 

 hair with its inner sheath (fig. 53, B.). The young hair, the point 

 of which at first does not project beyond its inner root-sheath, 

 gradually reaches with its point to the opening of the old hair- 

 follicle, whilst, at the same time, its root-sheath becomes elongated. 

 At length it passes out, and appears at the same opening with the 

 old hair, which, in the meantime, has been more and more pushed 

 upwards. When the development of the young hair is tints far 

 advanced, the last stage can be easily comprehended. The old 

 hair, which has long ceased to grow, and has lost its connection 

 with the bottom of the follicle, falls out; whilst the young hair 

 becomes larger and stronger, and fills up the vacuity left by the 

 old one. I regard the development of the above-described process 

 of the hair-bulb and outer root- sheath at the bottom of the follicle 

 as the primum movens of the death and shedding of the old hair. 

 As the follicles are not correspondingly elongated, the process in 

 question pushes upwards all the parts lying above it, and continually 

 increases the distance separating the hair-papilla from the proper 

 substance of the old hair, i. e., the part at which the round cells of 

 the bulb commence to elongate and to be converted into a horny 

 substance. Thus the hair is raised, as it were, from its nutrient 

 soil, receives a less and less supply of blastema, finally, ceases to 

 grow, and in its lowermost part, as well as above, is converted into 

 horny matter. The cells of the process, on the other hand, which 

 arc in connection with the papilla, continually draw new formative 

 material from it, which, for the time being, they use, not for the 

 formation of horny matter, but for their own growth. Thus the 

 intervening process attains a greater and greater length, and 

 pushes, in a purely mechanical manner, the old horny hair-root, 

 together with its sheath, quite to the aperture of the sebaceous 

 glands, where, to all appearance, a partial solution of the old 

 sheath takes place, which can be demonstrated with certainty in 

 the inner sheath, and must be presumed to take place in the outer 

 also. 



