190 SPECIAL HISTOLOGY. 



this by the foetus, and may afterwards be found in the meconium. A 

 proper shedding of the hair does not take place at all in the foetus, so 

 far as I can see, infants being born ■with the lanugo ; as little does any 

 trace of a further formation of hair appear after its complete eruption. 

 The question whether the point of the hair is first formed, or whether 

 the latter is developed at once as a whole, is readily solved. Hairs 

 which are just formed, have a bulb Avith soft cells, a horny point and an 

 intermediate portion, in which the cells are converted into horn, and 

 are partly found passing into the cells of the root, whence there can be 

 no doubt that we have here a whole hair. That the horny part of this 

 hair subsequently forms the point of a larger hair, is of no importance; 

 and as little as the hairs of the head of a newly-born infant can be 

 called points of hairs, because they subsequently become the points of 

 larger hairs, can we so denominate these. Nor can it be said that the 

 first foetal hair subsequently becomes, in totality, the point of a larger 

 hair, since the hairs do not grow by the simple apposition of new ele- 

 ments, like the bones, but by the multiplication of their lowest soft cells, 

 some of which are always retained as a reserve for cells to be newly 

 developed, whilst the others are converted into horn ; whence also it 

 happens, that the cells even of a complete hair-bulb are to be regarded 

 as the successors of those of the foetal hair.* 



* [From what has been said above (see note on the Cuticle) it is clear we do not share 

 Professor KoUiker's view that the hair is an epidermic production. Reichert's view, on the 

 other hand, that the hair results from the cornification of a dermic papilla or matrix, which 

 drying up and becoming filled with air, remains as the medullary portion, seems to us to be 

 nearer the truth. There can be no doubt of these two facts: 1, that no line of demarcation 

 can be traced between the papilla of the hair and its shaft; and 2, that in many animals 

 the papilla is vascular and nervous for a considerable distance into the shaft, and, therefore, 

 is certainly a dermic structure. 



Whether Reichert's somewhat mechanical notion of the " drying up" of the matrix to form 

 the medulla is correct, is not of much importance, so long as we keep in view the unques- 

 tionable continuity of tissue and honiological identity, of the medulla and cortex with the 

 dermic papilla. 



For us, in fact, the Hair is homologous in all its parts with the Tooth. The substance of 

 the shaft corresponds with the dentine, offering even rudimentary tubes in its aeriferous 

 cavities; the inner layer of the cuticle answers to the enamel, the outer to Nasmyth's mem- 

 brane ; and whoever will compare these structures will be struck by the similarity even in 

 their appearance. The sac answers to the dental capsule ; the outer root-sheath to the layer 

 of epithelium (enamel organ) next the capsule; the fenestrated membrane to the stellate 

 tissue ; and what Professor Kolliker calls " Huxley's layer," to the columnar epithelial layer 

 of the organon adamantince. The comparison may seem startling at first, but the examina- 

 tion of the development of the teeth of an osseous fish, for example, will suffice, we believe, 

 to afford full justification of it. 



With respect to the not very important question, as to the nature of the first rudiment of 

 the hair-shaft, i. e. whether it is the point of a hair or a whole hair, we must confess that we 

 should be tempted to arrive at the ojiposite conclusion to our author. Inasmuch as the por- 

 tion of the hair which first appears becomes the point of the fully-grown hair, we should 

 say that the hairs are formed like the teeth, point first. 



A hair, like a tooth, has a definite form to attain. As the latter has a peculiarly con- 



