EXHALATION AND ABSORPTION. 185 



outer covering, called the cuticle, or epidermis (the part raised by 

 blistering), which has no feeling, and little vitality ; and another 

 thicker part underneath, called the true skin (the part which tan- 

 ners convert into leather), which is plentifully supplied with nerves, 

 blood-vessels, &c. 



From what has been said, it will be seen that the mechanism of 

 exhalation is very simple, the fluid merely passing through the sides 

 of its vessels. In every part of the system an active absorption is 

 carried on by the same means, the fluid removed merely passing 

 through the sides of the veins, to be carried off by the internal cur- 

 rent. It was at one time supposed that absorption was exclusively 

 carried on by a system of vessels, which received the name of ab- 

 sorbents ; but this is now known to be quite incorrect. Allusion 

 has already been made to one portion of these absorbent vessels 

 connected with digestion, which are called lacteals. Similar 

 vessels in other parts of the body receive the name of lymphatics, 

 from a fluid called lymph, which they convey ; and in their course 

 towards the thoracic duct, in which they almost all terminate, they 

 pass through glandular bodies, found in numbers in the hams, 

 groins, armpits, on the sides of the neck, &c. It is these glands 

 about the neck that so often swell and inflame when there is disease 

 of the gums, or eruptions on the head, or when there exists a highly 

 scrofulous habit of body. 



The veins appear to take up all fluid matters indiscriminately that 

 are brought in contact with them ; the lacteals take up principally 

 (if not solely) chyle ; the office of the lymphatics seems to be chiefly 

 to mould the different parts of the body into their proper forms, and 

 the lymph contained in them is probably the removed animal mat- 

 ters, which, it is supposed, may undergo some changes while pass- 

 ing through the lymphatics and their glands, that render them fit to 

 be mingled with the blood. From the late researches of Fohmann, 

 Panizza, and Lanth, it would appear that the lymphatics commence 

 by minute plexuses, and that these at their origin do not communi- 

 cate with the arteries and veins, but begin by shut extremities. In 

 the frog, and in some other reptiles, there have been discovered 

 parts, connected with the lymphatics, that pulsate irregularly, like 

 hearts. The frog has four of these, which seem to be used for pro- 

 pelling the lymph. 



Absorption and exhalation, in a healthy state, generally balance 

 each other, so that a full-grown person's weight, notwithstanding 

 the quantity of food consumed, will frequently for years vary only 



