THE SKIN. 6 1 9 



viz., sensible or visible, and insensible or invisible perspiration. One or other of these states 

 is always present, unless sweating has been temporarily checked by disease. In the dog, however, 

 the sensible or visible perspiration is never present,* owing probably to the more open condition 

 of the mouths of the pores, which permit the sweat to be evaporated as soon as secreted ; and 

 this has given rise to the erroneous notion that the dog is an animal who never sweats, or 

 "sweats only with his mouth." 



Perspiration has it uses, two of which it may be sufficient to mention here. First it carries off 

 from the body matters which if retained would give rise to disease, as, for example, the poisonous 

 acid which is supposed to occasion gout and rheumatism ; and secondly, it cools the body when 

 heated by the process of evaporation, with which most people are well acquainted. 



The sebaceous or oil glands have a different office to perform. They secrete a fatty or 

 oily matter, which, through their tiny ducts, is poured into the tube from which the hair grows, 

 lubricating not only this passage, but creeping out and along the hair itself, down to its very end. 

 The coat of the dog is thus protected from wet or moisture. In some dogs this secretion is more 

 abundant than in others. It is especially so in the Newfoundland and in the Scottish Collie. 

 It is also more abundant in health than in disease ; its absence gives rise to the harsh, dry, staring 

 coat we see in dogs that are suffering from illness. 



The hair-follicles are the tubes in which the hairs grow. At the bottom of each tube is 

 situated a small vascular papilla or elevation, and on this the hair is planted. A hair is 

 simply a quill on a small scale, being supplied with nutrition and colouring-matter from the 

 papilla on which it grows. 



The thickness of the skin varies on different parts of the body. On the back, head, chest, and 

 indeed on every portion requiring protection, it is thick ; on the inside of the thighs and lower part 

 of the abdomen it is much thinner, and to this arrangement may be attributed the fact that 

 eruptions are much more common on the latter regions. 



The principal use of the skin is to form a protective envelopment to the whole body, which, 

 although permitting the free exit of the perspiration, is still proof against the absorption of many 

 of the most virulent of poisons. 



On the other hand, it must not be forgotten that the skin is to a certain extent an absorbent. 

 It has been proved beyond question that the skin is even, in some measure, a respiratory organ, 

 and this in itself should convince us of the value of keeping our animals as much as possible in 

 the pure open air, and the danger of keeping them shut up in badly-ventilated kennels or 

 apartments ; for the skin is just as capable of absorbing deleterious as non-deleterious gases or 

 matters from the atmosphere surrounding it. The absorbent power of the skin is retarded by 

 the cuticle; it is the inner or true skin that is so highly absorbent, that we often introduce 

 medicines such as morphia or belladonna through it into the system, having first removed the 

 cuticle by blistering. 



Having seen how delicately constructed the skin is, and how sentient, with its bundles of 

 arteries, veins, and nerves, its delicate glands, its minute pores over 2,OOO to the square inch 

 and even its tiny muscular system, we need not wonder that it is very liable to disease in itself, 

 and also, if its secretions be interfered with and checked, that it becomes the cause of disease 

 in other organs of the body. 



In this division of the treatise we shall content ourselves with describing 



I. The more common non-contagious diseases. 



* Except in cases of fever, when it is abundant on the inside of the thighs. 



