CUTANEOUS SYSTEM. 



'2-21 



the body : so that, besides being the organ of touch 

 the function of the skin is vicarious with that of the 

 lungs, serving to remove the superfluous carbon from 

 the system. It serves the same purpose even with 

 fish ; for Spallanzani and Provencal found that the 

 skins of fish produced carbonic acid as well as their 

 gills. Although in plants an epidermis or cuticle, and 

 envelope analogous to the rete mncosum, is found to 

 exist, they do not appear to possess any integuir.ent 

 analogous to the cutis vera, which, in descending the 

 scale of organisation, may be said to terminate with 

 the Crustacea. The skin then of animals is found to 

 consist of these three layers, which, when chemically 

 examined, are discovered to be composed almost en- 

 tirely of gelatine, an animal principle which united 

 with tannin, forms the remarkable substance leather. 

 When the skins, therefore, of animals are macerated 

 in bark, the tannin of the bark, uniting chemically 

 with the gelatine of the skins, forms this compound, 

 which is insoluble in water, resists putrefaction, and 

 becomes hard and tough when dry. 



The cutaneous system of animals and vegetables 

 comprehends also, as already mentioned, the appen- 

 dages to the skin ; such as hair, wool, horn, feathers, 

 shells, &c. HAIR is common to all mammalia, whales 

 not excepted ; it also occurs, mixed with feathers, 

 round the head and neck of certain birds ; it is, how- 

 ever, absent in reptiles, fish, and mollusca, although 

 found to exist in many annulose animals, and even 

 zoophytes. Every individual hair may be described 

 as consisting of a hollow tube proceeding from a root 

 or bulb below the cuticle, and terminating in a very 

 fine point. The bulb is of an ovoidal shape, and con- 

 sists of an external and internal covering the former 

 b*ing composed of condensed cellular tissue; the latter 

 being a simple membrane which lines the interior of 

 the tube. The cuticle introduces itself into the bulb, 

 and having become attached to the hair at its root, is 

 reflected back again ; hence the hair holds firmly to 

 the skin. The tube arising from the bulb is filled 

 with a soft matter called the medulla or pith of the 

 hair, which is the seat of a kind of imbibition whereby 

 the colouring matter secreted by the vessels of the 

 bulb is raised so as to give an uniform colour to each 

 individual hair. The human hair is generally either 

 black, brown, auburn, yellow, or red ; besides which 

 a white variety characterises the race of people termed 

 Albinos. When the vessels which secrete this colour- 

 ing matter, and which also nourish the hair, become 

 debilitated or when the secretion is interrupted by 

 any violent, mental emotion, the hair turns grey, or 

 becomes purely white. This happened, it is well 

 known, to the unfortunate Louis XVI. of France, the 

 nijjht previous to his execution ; also to Marie 

 Antoinette, the queen of France, whose hair became 

 white during the period of her journey fromVarennes 

 to Paris. It also occurred to the unhappy queen 

 Mary ; and many other cases of a similar description 

 are on record. Sometimes even after the hair has 

 turned grey during a period of affliction, it will after- 

 wards recover its natural colour and this loss and 

 recovery of colour has occurred to some persons in a 

 verv short space of time. Black hair has been gene- 

 rally considered significant of a vigorous constitution ; 

 white, on the contrary, was called by Lord Bacon the 

 " colour of defect," and is regarded as a sign of de- 

 bility. Hence, horses with white feet, are thought 

 to be more tender and susceptible of disease than 

 those of a more uniform dark colour. When the ves- 



sels which nourish the roots of the hair become debili- 

 tated, as in extreme old age or after sickness, the bulb 

 collapses, its attachment to the skin is destroyed, and 

 the hair is shed. This sometimes occurs irresnlarly 

 and in patches : sometimes the disease is universal, and 

 not a hair remains on the surface of the body. This 

 occurred to the chevalier D'Eperney, who, after four 

 months' studious application, and without any illness, 

 lost his beard, eyebrows, eyelashes, and all the hair of 

 his head and body. Certain kinds of diet, especially a 

 fish diet, is said to produce baldness. In the Shetland 

 islands, so common was baldness formerly, that it was 

 a common saying that "there was not a hair between 

 them and heaven." Tournefort relates, that in the 

 island of Mycene the inhabitants seldom arrive at the 

 age of twenty- one without becoming so. There are 

 some races of people that have little or no hair on the 

 surface of the body. The Mongolian, Chinese, and 

 American have little or none upon the chin or chest. 

 Hair varies considerably in shape, texture, and in all 

 its mechanical properties. Instead of being cylindri- 

 cal, it is sometimes flattened, striated, and deeply 

 grooved, or even beaded. It also varies much in 

 length, firmness, tenacity, and disposition to curl ; all 

 which varieties depend on some corresponding differ- 

 ence in the relative action of the vessels at the bull) 

 or root. The human hair which is most esteemed in 

 commerce, is about twenty-five inches in length ; and 

 the more it falls short of this, the less value it bears. 

 Its length and quantity is, in all animals, much inliti- 

 enced by change of season and climate. Previous to 

 winter, the hair increases in length and quantity, and 

 this increase bears a ratio with the temperature ; hence 

 cattle and horses in farms near the level of the sea, 

 have a shorter and thinner hair than those in higher 

 elevations, where the temperature of the air is lower. 

 The fur of animals, which is sought as an article of 

 commerce, is thin, and would be less valuable if ob- 

 tained during the summer than during the winter sea- 

 son. The influence of climate is still more obvious. 

 The dogs of Guinea, and African and Indian sheep* 

 possess so little hair on the body, that they may be- 

 almost said to be naked ; the Siberian dog and Ice- 

 and sheep are, however, protected by a very long and 

 thick covering. The fleece of sheep in England is, 

 entirely wool ; the Zetland and Iceland sheep, how- 

 ever, in addition to wool, have intermixed with it a 

 quantity of coarse and shaggy hair. In warm coun- 

 tries the elephant and rhinoceros have scarce any 

 lair ; on the contrary, the carcases of those discovered 

 n the ice of Siberia, are found covered with a sort of 

 wool mixed with long thick hair, very similar to the 

 oat of the Iceland sheep. To accommodate them- 

 selves to this change of season and climate, animals 

 :ast and renew their hair, just as birds moult, or as 

 lerpents and caterpillars cast their skin. Moles cast 

 heir winter clothing generally before the end of June. 

 The fleece of sheep, if allowed to fall, is generally cast 

 Before the end of July. 



In some cases the nerves which supply the roots 

 of the hair serve to extend the sense of touch ; 

 thus the hairs which form the whiskers of the lion, 

 tiger, and cat, being supplied with pretty large 

 nerves at their roots, the slightest impression is com- 

 municated from their joint to their base. It is the 

 same with the whiskers of the seal. The hairs of 

 he whiskers are moved freely at the will or pleasure 

 jf these animals, which is not the case with the hairs 

 ot the rest of the body, although under certain vio- 



