ABSORPTION. 



by bringing one of the parts within the other's ranyc 

 of action. 



When the process extends no further than absorp- 

 tion, it belongs to chemistry, and not to natural history, 

 for chemistry holds the same place in the mineral 

 kingdom which physiology does in the animal and the 

 vegetable ; and as in these absorption is only one 

 part of the physiological process, and that a preliminary 

 one, which in itself produces no result, the modifica- 

 tion of it can be better explained in treating of those 

 ultimate actions to which it is preliminary. 



When the absorbed substance is a liquid, it is 

 generally taken up by vessels which are, from the 

 offices which they perform, called absorbents, or by 

 apertures in a membrane, which are called pores ; but 

 there appear also to be absorbing surfaces, in which no 

 pore is discernible either by the eye or the microscope. 

 Plants absorb water by the spongclets or little sponges, 

 upon the rootlets, or young fibres of their roots ; but 

 they also absorb by their leaves, and, in many in- 

 stances by their whole surface, even though, when 

 examined by the microscope, what appear to be pores 

 on their surface seem rather to be cuts de sac, or 

 small indentations, lined throughout with the unbroken 

 epidermis of the plant. When a plant thus absorbs, 

 it revives ; and the same takes place with animals, and 

 even with man himself. If one who is parched with 

 drought stand over water, and especially with the bare 

 feet immersed in it, thirst is allayed, and the body re- 

 covers its tone, in a manner similar to that in which a 

 lopped twig or a pulled flower recovers, when it is 

 sprinkled with or nipped in water, or when the stem 

 of it is placed in that fluid. 



There are, in the case of the human body, some 

 other circumstances, which not only prove the ex- 

 istence of an intellectual principle, totally different 

 from the body, but which show that that principle can, 

 of itself, to a certain extent, sustain the body and allay 

 its anguish. When one has been long upon the dry 

 hill, fatigued, exhausted and parched, the sight of a 

 running stream, or even the sound of a waterfall, will 

 revive the spirits, and bring at least a momentary relief, 

 as the author of this article has often experienced. 

 The duration is, no doubt, fleeting ; and though the 

 observations of Shakspeare are as philosophic as they 

 are practical, for 



" Who can hold a fire in his hand, 

 By thinking on the frosty Caucasus ? 

 Or wallow naked in December's snow, 

 By thinking on fantastic summer's heat ?" 



yet still, such is the power of the mind over the body, 

 that both the eye and the ear can absorb relief, in 

 cases where there can be no material contact. 



In the action of vegetables, the whole preliminary 

 part of the process appears to be absorption ; and, 

 though in many instances the mode eludes our most 

 careful observation, they can, in the greater number of 

 the species, feed at the whole of the active surface when 

 in leaf, they do not in any instance take food into 

 an organ at all analogous to what we call the stomach 

 in animals. From this, it should seem that, with them, 

 nourishment passes more immediately to organisation, 

 without the process of assimilation. Excepting in the 

 ease of poisons, which both plants and animals seem 

 capable of absorbing, and which they absorb at dif- 

 ferent parts, according to their nature, plants do not 

 appear to take into any part of their system substances 

 which are not wholly available for the purposes of 

 vegetable life and growth. They no doubt give out 



gases, and different ones, according to circumstances ; 

 but there is still a difference of opinion even amongst 

 the most eminent botanists as to whether they give 

 out any extrementitious matter, either in a solid 

 or a liquid state; and the gases which they give 

 out bear more resemblance to those given out by ani- 

 mals in respiring, or in some other process posterior to 

 assimilation, than to the mutters which are rejected 

 by the animal system in that process. 



The power of absorption, in organised substance-. 

 increases nearly in the ratio of the complexity of their 

 organisation. Plants absorb less than animals ; and 

 among these those of the simplest structure absorb the 

 least. There appears to be, vn the living subject, only a 

 very limited power of election of what matter it shall 

 or shall not absorb. Absorption can separate mechani- 

 cal mixtures ; but it is doubtful whether it can effect 

 any chemical solution. Air and water are the sub- 

 stances most generally absorbed by the external sur- 

 faces both of plants and of animals ; and in the case 

 of water, any foreign substance with which it happens 

 to be mechanically mixed is generally left behind. 

 When sailors are long exposed without water they can 

 quench their thirst by plunging themselves into the 

 sea, or by wetting their clothes with sea water ; and if 

 the relief is obtained by so wetting the clothes for a 

 long time, these become impregnated with salt to a 

 much greater extent than if they had been kept the 

 same length of time in saltwater, without being in con- 

 tact with the absorbing surface of the body. If, when 

 one is in a boat at sea in very hot weather, the arm, 

 even the hand only< is placed in the water, an agree- 

 able freshness diffuses itself over the whole body, and 

 the part immersed gradually becomes covered with an 

 incrustation of salt. 



The - sea fogs, which are evaporated, especially 

 from flat beaches upon which the tide water alternates, 

 in the early part of the season, can hardly be said to 

 be salt ; but when they settle upon vegetables, the 

 leaves and other surfaces of these absorb the water, 

 and the salt remains, so that, after a few hours of a 

 thick fog, it is very perceptible to the taste. Up to a 

 certain point, that process is wholesome ; and the 

 crops and hedges seem as much revived as if the 

 humidity had descended limpid from the sky ; but if 

 it continues long, and the sun breaks out so as to 

 evaporate the remaining moisture quickly, the salt 

 corrodes and destroys the leaves. It appears to do 

 that more readily and completely in proportion as the 

 leaves are of a more absorbent structure ; and hence 

 the difficulty of getting many species of plants to grow, 

 if exposed to the sea air. City fogs have even a more 

 pernicious effect upon vegetables than saline fogs 

 from the sea ; because the salts with which they aro 

 loaded are of a more caustic nature ; and because 

 some of them are absorbable by the plants, and thus, 

 though they do not instantly kill them, they injure 

 their qualities. Culinary vegetables which are grown 

 within the reach of those fogs are very inferior in 

 flavour to those grown in pure air, even though the 

 soil and mode of treatment may be very much inferior. 



Evaporation, or the taking up of humidity by the 

 atmosphere, is a species" of absorption, and follows 

 the same law. Common salt does not rise and mingle 

 with the air in that process ; but the more pernicious 

 matters which pass into the state of gas at low tem- 

 peratures do ; and hence the invisible vapour which 

 rises from the sea is usually limpid and wholesome, 

 while the effluvia of marshes and other places, where 



