554 DES. &EORGE ANT) FEAKCES E. HOGGAN OS 



and in the same animal. A little way below the opening of the 

 hair-follicle upon the skin, we have the opening into the follicle 

 of a little sac or gland lined with cells (s, fig. 6, Plate XIII.) ^ 

 which secrete the grease of tlie skin. This sac is called the 

 hair-gland or sebaceous gland. It is immediately underneath the 

 level of the opening of this gland into the hair-follicle that the 

 nerve-terminal apparatus is found. Finally, attached to the bottom 

 of the hair-follicle, and passing somewhat obliqely toAvards the 

 epidermis, we have the bundle of muscle-fibres which act upon the 

 hair and gland *. 



* Although not quite pertinent to our present paper, we wish to give a cau- 

 tion against merely considering the hair as a tactile organ, as it seems to have 

 several functions to perform, although only one other, that of a covering, seems 

 to be attributed to it in our physiological text-books. Some years ago, when 

 teaching anatomy in Edinburgh, one of us was careful to inculcate upon our 

 students those various uses of the hair and hair-apparatus, which we may here 

 recapitulate. In the first place, the hair has a double fmiction to perform on 

 the great mass of the human skin, altogether apart from either being a covering 

 or a tactile agent. It is a stylet, which keeps the mouth of the hair-follicle 

 always clear for the comparatively inspissated material to flow from the sebaceous 

 gland on pressure by the compressor muscles upon the surface of the skin ; and 

 at the same time it is a semicircular valve, similar to that known to marine 

 engineers as a D valve, which occludes the mouth of the sebaceous gland when 

 that gland is quiescent, preventing ingress of foreign matters into the gland ; 

 but when the compressor muscle contracts and compresses the gland, the same 

 movement moves the hair valve from the mouth of the gland, leaving a space also 

 between it and the hair-follicle, so as to permit egress to its sebaceous contents. 

 According to this way of thinking, the gland is not an appendage of the hair, 

 as is generally supposed, whence its name of hair-gland. It is an appendage of 

 the skin ; and the hair itself is only an appendix to the gland. 



In the same way the so-called hair-muscle, the erector or arrcctor fili, we con- 

 sider not to be an appendage of the hair, as its name implies, but an appendage 

 of the sebaceous gland ; and hence, ten years ago, we proposed to call it, and 

 always called it, the compressor glanclula sebacecB, from its evident action of acting 

 as the compressor of the sebaceous gland, and the excretor of its tliick con- 

 tents. That this muscle, on contracting, should cause goose-skin by depressing 

 the skin at one of its extremities of attachment, and that it should cause the 

 hair to protrude and lie at right angles to the surface at its other extremity of 

 attachment, are merely accidental phenomena attendant upon the performance 

 of its fvmction, not the functions performed by the muscle, and ought, therefore, 

 never to have given a name to the muscle. That the hair acts specially as a 

 stylet, is seen also in the sebaceous glands or their analogues on certain moist 

 surfaces of the body, which, from the fact of being moist, are never liable to 

 become blocked up, and therefore the hair, being unnecessary as a stylet or 

 valve, is not present. 



