200 SPECIAL HISTOLOGY. 



out after a severe illness, are replaced, it is more probable, since, 

 according to E. H. Weber, the sacs of lost hairs remain for a 

 long time, that they arise in the old sacs, than that new ones 

 are developed. 1 



[The multiplication of the cells of the bulb of the hair 

 during its growth takes place unquestionably, not by free cell- 

 development, since no trace of anything of the kind is to be 

 seen in any bulb, but either by endogenous cell-development 

 round portions of contents, or by division. I do not think that all 

 those hairs which possess a sharply-defined clavate bulb are on 

 that account dead and ready to fall out. It is certainly thus in 

 many cases; but in others this condition indicates nothing more 

 than the normal termination of growth, whence of course, it does 

 not follow that the nutrition also has ceased. In proof of the 

 occurrence of a continual development of the hairs indepen- 

 dently of the old hair-sacs, the hairs which lie spirally curled up 

 under the epidermis and subsequently break thi'ough it, upon 

 the forearm, leg, &c, are frequently cited. But I do not 

 know that it would not be more correct to consider this, with 

 many pathologists, rather as an abnormal process. In the first 

 place this formation of the hairs by no means occurs in all 

 persons; and secondly, where it does, there are found together 

 with those coiled-up hairs, which are apparently normally 

 developed, others which are evidently abnormal, in great 

 Quantities. These, often in considerable number (up to 9), with 

 thick sheaths, lie in one sac and have rounded points, with 

 irregular bulbs. With respect to their relations, it might for 

 the present be wiser, so long as an actual, normal new develop- 

 ment of hairs has not been demonstrated, not to assume it, 

 and to consider that, even at a later period, the development of 

 new hairs within the old sacs is the normal mode, especially 

 since Dr. Langer has actually observed it to take place in many 



1 [Bertliolil (Mull. 'Archiv.,' 1850) has communicated some curious statistics 

 relative to the growth of Hairs. The hairs of the head of a female of from 16 

 lo 24 years of age, grow at the rate of 7 lines a month. The growth of the 

 hairs of the heard is quicker the oftener they arc cut; shaved every 12 hours, 

 they would attain a length of from 5.^ — 12 inches per annum ; every 24 hours, from 

 5 — 7', inches; every 36 hours, from 1 — 6^ inches. They grow faster by ,' s during the 

 day than during the night: and in 18 days of Summer, (V02G more than in 18 days 

 of winter. — Eds 



