294 HORSE, SWINE AND POULTRY DISEASES 



scales, hairs, horn, sebaceous matter, sweat, and other excretory 

 matters, that any extensive disorder in its functions may lead to 

 serious internal disease and death. Again, the intimate nervous 

 sympathy of different points of the skin with particular internal 

 organs renders certain skin disorders causative of internal dis- 

 ease and certain internal diseases causative of affections of the skin. 

 The mere painting of the skin with an impermeable coating of glue 

 is speedily fatal ; a cold draft striking on the chest causes inflamma- 

 tion of the lungs or pleura ; a skin eruption speedily follows certain 

 disorders of the stomach, the liver, the kidneys, or even the lungs; 

 simple burns of the skin cause inflammations of internal organs, and 

 inflammations of such organs cause in their turn eruptions on the 

 skin. The relations nervous, secretory, and absorptive between 

 the skin and internal organs are most extensive and varied, and 

 therefore a visible disorder in the skin may point at once and speci- 

 fically to a particular fault in diet, to an injudicious use of cold water 

 when the system is heated, to a fault in drainage, ventilation, or 

 lighting of the stables, to indigestion, to liver disease, to urinary dis- 

 order, etc. 



STRUCTURE OF THE SKIN. 



The skin consists primarily of two parts: (1) The superficial 

 non-vascular (without blood vessels) layer, the cuticle, or epidermis; 

 and (2) the deep vascular (with blood vessels) layer, the corium, 

 dermis, or true skin. The cuticle is made up of cells placed side by 

 side and more or less modified in shape by their mutual compression 

 and by surface evaporation and drying. The superficial stratum 

 consists of the cells dried in the form of scales, which fall off continu- 

 ally and form dandruff. The deep stratum (the mucous layer) is 

 formed of somewhat rounded cells with large central nuclei, and in 

 colored skin containing numerous pigment granules. These cells 

 have prolongations, or 'branches, by which they communicate with 

 one another and with the superficial layer of cells in the true skin be- 

 neath. Through these prolongations they receive nutrient liquids 

 for their growth and increase, and pass on liquids absorbed by the 

 skin into the vessels of the true skin beneath. The living matter in 

 the cells exercises an equally selective power on what they shall take 

 up for their own nourishment and on w r hat they shall admit into the 

 circulation from without. Thus, certain agents, like iodine and 

 belladonna, are readily admitted, whereas others, like arsenic, are 

 excluded by the sound, unbroken epidermis. Between the deep and 

 superficial layers of the epidermis there is a thin translucent layer 

 consisting of a double stratum of cells, and forming a medium of 

 transition from the deep spheroidial to the superficial scaly cuticle. 



The true skin, or dermis, has a framework of interlacing bun- 

 dles of white and yellow fibers, large and coarse in the deeper layers, 

 and fine in the superficial, where they approach the cuticle. Be- 

 tween the fibrous bundles are left interspaces which, like the bun- 

 dles, become finer as they approach the surface, and inclose cells, 

 vessels, nerves, glands, gland ducts, hairs, and in the deeper lay- 

 ers fat. 



