CHAP, xiv.] THE CUTIS. 407 



it is probably this element also which is principally concerned in the 

 changes the skin undergoes during the process of tanning. The 

 varieties in the qualities of different skins for this purpose might be 

 explained by a reference to these two varying elements of their 

 fibrous framework. In the museum of King's College is a specimen 

 of excellent leather tanned from the skin of Bishop, one of the 

 murderers of the Italian boy who fell a victim to the infamous 

 system of " Burking" many years since. 



Some anatomists have thought that the contractility of the skin, 

 manifested under the influence of cold, and even under certain 

 emotions, is due to the existence of peculiar fibres ; and Gerber 

 has very recently figured what he considers to be such fibres. He 

 describes them as begirting the hair-bulbs. 



There is good reason for believing that these fibres, if they exist, 

 do not essentially differ from those of unstriped muscle ; for in the 

 dartos we have found the latter intermingled with an abundant and 

 lax areolar tissue : and the close resemblance between the contrac- 

 tion of the scrotal membrane and that of the skin has been gene- 

 rally recognised. In fact, the dartos seems to be nothing more 

 than a modification of the dermoid and subdermoid tissue, of which 

 the principal peculiarities are the excess of this form of muscle, the 

 laxity of the meshes, and the absence of fat. It is probable, also, 

 that the phenomenon of " erection " of the nipple is due to the 

 contraction of similar fibres.* 



The thickness and strength of the cutis, or areolar framework of 

 the skin, differ greatly in different parts, according to the amount 

 of resistance required against internal or external pressure. On 

 the hinder surface of the body it is denser than in front, and on the 

 outer than on the inner surfaces of the limbs. It is unusually thin 

 over the flexures of the joints. It is particularly delicate in the 

 eyelids, and proportionally so in some other situations, where great 

 mobility is demanded. In regions which are most subject to ex- 

 ternal pressure, as the soles of the feet, it is firmly united by very 

 dense laminae to the subcutaneous fascia ; and the intervals between 

 these are provided with pellets of fat, forming a cushion, as an ad- 

 ditional means of protection to the delicate organs it encloses and 

 covers. 



Among the lower animals, we may notice numberless examples of 

 an analogous kind. One of the most striking is that of the great 

 whales, which, being liable to enormous pressure on the surface of 



* Cyclop, of Aiiat. and Phys. vol. iii. p. 518. 



