170 THE COMMON INTEGUMENTS. 



in every part : on some its quantity is considerable, as on 

 the back and extremities ; and on otliers it is very thin, as 

 over the hps, &c. It is much increased by pressure. Over 

 the knees, the points of the elbows, and hocks, it becomes 

 likewise much increased from this cause, or by the animal 

 constantly rising and lying down. Within the fore arm, 

 and on the inner side, behind the cannon, it produces a 

 substance not unlike horn, which grows to a considerable 

 length, and falls away in scales. The cuticle is a secre- 

 tion of the cutis, and adheres firmly to the numerous papillae 

 of its matrix. The cuticle may be separated by maceration 

 and by boiling in the dead subject ; in the living, by frictions 

 and stimulants, as blisters. It covers the skin throughout 

 its whole extent, except at the hoofs, which it is probable 

 are themselves only a species of cuticle, and hair assuming 

 another form. The cuticle is also continuous with the epi- 

 thelium, or outer covering of mucous membrane, with 

 which it blends at the eyes, nose, mouth, and anus. The 

 cuticle is perforated by the perspiratory ducts ; and by 

 sebaceous glands, opening within the tubes that shelter the 

 bulbous extremities of the hairs. Through the perspiratory 

 orifices, the insensible perspiration passes off; and through 

 the sebaceous glands, the cuticle is furnished with an unc- 

 tuous substance which keeps it soft and pliant. Blisters ap- 

 plied, irritate and inflame the true skin, and occasion so 

 great a deposit of serum underneath, that, the cuticle being 

 impervious, the external covering is raised by its pressure 

 in bladders. The insensible skin is speedy in its repro- 

 duction, forming itself anew in a very short time after its 

 removal from a healthy surface. 



The rete mucosum is nothing more than the first secretion 

 of the cuticle. The cuticle is secreted in minute ovoid 

 bodies, that in their new state contain a certain quantity of 

 pigment. This pigment is lost as the secreted cuticle is 

 pushed upwards ; while the particles, from being ovoid, be- 

 come more and more flattened, till, upon reaching the sur- 

 face, they have become quite flat, quite colourless, and fall 

 off, as scales, or scurf. 



The cutis, or true skin, is a very highly organized mem- 

 brane, whether we regard its vascularity, sensibility, or the 

 intimate reticulation of its fibres. Its density of structure 



