PHYSIOLOGY. 



papilla:, endued with greater sensibility 

 and vascularity, and thereby constituting 1 

 in a more especial manner organs of 

 touch. This is the case with the hands. 

 The number of bones that compose these 

 organs render them susceptible of infi- 

 nitely varied motions, and enable them 

 to explore with accuracy the surfaces of 

 the most unequal bodies. The soft ends 

 of the fingers receive large nerves and 

 arteries, and possess very numerous and 

 prominent papillze. This finely organized 

 skin is formed into a gently convex pro- 

 tuberance, by an accumulation of a soft 

 fat under it, and it is defended and sup- 

 ported by the nail ; and accordingly these 

 pulpy extremities of the fingers are en- 

 dowed with the most refined sense of 

 touch. The lips and the glans penis have 

 a similar structure, and receive from this 

 organization a very exquisite sensibility, 

 which is a modification of touch. 



As the cutaneous papillae are covered 

 by the epidermis, it follows that the very 

 superficies of the body is insensible. The 

 cuticle and its appendages, the nails and 

 hair, have neither vessels nor nerves, and 

 possess no powers of life or growth in 

 themselves. It forms a medium, mode- 

 rating the impressions which would be 

 too vivid from an absolute contact of sub- 

 stances ; when preternaturally thickened, 

 as in the hand of the labourer, it obstructs 

 sensation ; and when entirely removed, 

 as by a blister, the contact of bodies ex- 

 cites pain. It is also important in pre- 

 venting the action which the atmosphere 

 would otherwise exert in drying the sur- 

 face of the body ; when removed in the 

 dead subject the skin immediately be- 

 comes horny, and the same effect extends 

 more or less to the subjacent parts ; in 

 the living body its removal is followed by 

 incrustation or scabbing 



The skin is also to be considered as an 

 organ of secretion, and perhaps of ab- 

 sorption. Under the former head we 

 view it as the means of separating and 

 expelling from the body extraneous mat- 

 ters, whose retention would be injurious 

 to the system. This may be proved by 

 eruptive disorders, by the odours of 

 musk, garlic, &c. which affect the per- 

 spiration ; by the phenomena of sweating, 

 &c. by the injurious effects on the sys- 

 tem at large, which a suppression of the 

 cutaneous secretion causes, and the relief 

 experienced by sudorific remedies m 

 various cases. 



The secretion from the skin has been 

 divided into the sensible and insensible. 

 An abundant vapour continually exhales 



from the whole surface, and has the name 

 of insensible transpiration, or perspira- 

 tion, when it is invisible to the naked 

 eye, and passes off in the state of gas ; 

 but it is called sweat, when, becoming 

 more copious, it flows in form of a liquid. 

 The innumerable arteries, which pervade 

 every part of the skin, are the source of 

 these secretions ; and their exhaling eri- 

 fices are supposed to penetrate the cuti- 

 cle in a state far too minute for any means 

 of research that we possess. If the naked 

 body be placed against a white wall in 

 the sun during the summer season, a sha- 

 dow produced by the cutaneous exhala- 

 tion may be perceived; and the following 

 is also a decisive experiment to the same 

 point. Apply the end of the finger near 

 a glass or finely polished metallic instru- 

 ment, and the body will soon have its 

 surface tarnished by a vapour, which is 

 dissipated when the finger is removed. 



A great resemblance exists between 

 the cutaneous and pulmonary secretions ; 

 both are simple arterial exhalations, and 

 the mucous membrane of the aerial pas- 

 sages is a continuation of the skin. The 

 two secretions counterbalance each other; 

 and the connection between them is evi- 

 denced by the remarkable distress of 

 breathing attendant on extensive burns. 

 There is a similar connection with the 

 mucous exhalation of the intestinal canal ; 

 and a still more remarkable one with the 

 kidneys. 



The quantity of the insensible perspi- 

 ration appears by experiments to be very 

 great. Sanctorius, a Venetian physician, 

 who first noticed its importance and ex- 

 tent (whence it has acquired the name of 

 perspirabile sanctorianum) estimated it 

 at five pounds in twenty -four hours, when 

 the solid and liquid food amounts to eight 

 pounds. In temperate climates it may 

 be from two to four pounds daily ; but it 

 varies according to numerous circam- 

 stances. 



The chief bulk of insensible transpira- 

 tion and of sweat is water; it holds seve- 

 ral salts in solution. Carbonic acid gas 

 is also found in considerable quantity ; 

 and even according to some experiments, 

 azote and hydrogen. An oily or seba- 

 ceous matter is secreted from the skin, 

 to preserve the cuticle in a proper con- 

 dition of suppleness ; hence water is 

 repelled from the naked body, when 

 thrown on it. There are also some vola- 

 tile and odorous particles furnished from 

 the same source, in which the peculiar 

 smell of individuals and of nations re- 

 sides. 



