170 EXTRACTS AND ABSTRACTS FROM FOREIGN JOURNALS. 



that this is the root of the young hair, is, that in no follicle containing 

 pigment cells, was the mere point of a hair ever found, but the young 

 hair always appeared complete, though very small. In those sacs which 

 were not lined with dark pigment cells, the hair had the appearance of 

 terminating in very minute fibres, but this was without doubt owing 

 to the transparency of the cells of which the root of the hair is com- 

 posed. Henle and Bidder's opinion, that the hair is formed from the 

 cells at the bottom of the hair sac, is very probable, but most likely, 

 the nuclei of the cells undergo the transformation into the fibres of the 

 hair, and not the cells themselves, as Bidder imagined. 



After the hairs have acquired such a length as not to be capable of 

 being contained in the sac, they become bent into loops in such a man- 

 ner, that while the point and root of the hair are near each other, at 

 the bottom of the sack, the top projects out of the cavity. This condi- 

 tion of the hair existed in embryos seven or eight inches long ; in others 

 from eight to twelve inches in length, the points of the hairs, and part 

 of their shaft projected from the sac, but were covered by a membrane 

 which invests the whole foetus, and which was imagined by Isben to be 

 a prolongation of the amnion. To this notion, notwithstanding some 

 difficulties which oppose its adoption, Dr. Simon inclines. 



In addition to the true sac, all the hairs of the embryo of the swine 

 have a second investment contained within it, and analogous to that 

 part which Henle termed the sheath of the root, in his description of 

 human hair. This sheath is perceptible in hairs which are still entirely 

 contained within the follicle, when it presents the appearance of a 

 transparent line on either side of the hair. In no instance, however, 

 were any traces of this sheath perceptible before the hair was formed. 

 The sebaceous follicles connected with the hair sac, exist before the 

 formation of the hair. They differ in structure from the sebaceous fol- 

 licles in the full-grown pig, and consist of an elongated pouch, appa- 

 rently divided into compartments by transverse lines, and occupying the 

 upper part of the hair sac. One end of this pouch terminates close 

 under the opening of the hair sac by a conical or elongated point, and 

 its lower extremity is composed of an appendix of round granules bear- 

 ing some resemblance to a bunch of grapes. When the hair follicle 

 contains a young hair, this appendix is frequently divided by it into two 

 lateral lobes, which project beyond the borders of the hair follicle on 

 either side. Each of these lobes, which still retains the appearance of 

 being composed of rounded granules, continues connected with the 

 pouch, either immediately, or by means of a delicate prolongation, di- 

 vided, like the pouch itself, into transverse compartments. Whether 

 these sebaceous glands undergo subsequent metamorphoses, by which 

 they are brought to resemble the condition of those parts in the adult 

 animal, or whether new follicles are formed when the foetal hairs drop 

 out, and the bristles begin to be developed, has not yet been ascertained. 



Dr. Simon confirms the opinion that a distinct cortical and medul- 

 lary substance exists in the hair ; though when the hairs are black, the 

 cortical substance presents as dark a colour as the medullary matter. 

 He instituted experiments on the human hair to disprove Mandl's recent 



