132 ANIMAL. 



absorption alone. The mouth is a cavity of proper for this purpose are expelled, all of 



extremely varied character and construction these are wanting among vegetables, 

 adapted universally to the circumstances in 



which animals exist. Nothing analogous to a There are yet other processes which form an 



mouth is met with in any vegetable. essential item in the acts by which organized 



The food having been selected and seized is beings universally continue their existence, 



next transferred to the cavity in which it un- which it is necessary we should include in this 



dergoes an elaboration that fits it to be received summary of the common, particular, and dis- 



into the proper system of the animal and con- tinguishing attributes of vegetables and ani- 



verted into its own substance. We do not mals. One of the most important of these is 



find anything like the pouch denominated a Respiration. The leaves in the more per- 



stomach in any member of the vegetable king- feet vegetables are the instruments of respi- 



doin. The matter fitted for its nourishment, ration; their place is supplied by the general 



absorbed by the root, is transmitted to the surface in those plants that are aphyllous. Vege- 



stem, and from thence makes its way into the tables that live in air act immediately by 



leaves of the vegetable. It does not pass un- means of their respiratory organs upon the 



changed, however, from the earth into the root, ambient medium ; those that live in water, 



or at least it has advanced but a very short way upon the air held in solution by the fluid 



on its course to the leaves, before it is found around them. 



to have undergone certain changes, which are Vegetables are well known to exhale abun- 

 also known to be greater in amount as it is dantly from the surface of their leaves, or 

 examined at a greater height or distance from stems, in case they have no leaves. The mat- 

 the root. Although growing from the same ter exhaled is principally water. They have 

 soil too, the sap of vegetables, i. e. the fluid also the farther property of decomposing one 

 which is passing upwards through the woody of the elements of atmospheric air, namely, 

 fibres, is found to be universally different, carbonic acid gas. In the sunshine the leaves 

 Whether the peculiar qualities thus acquired of vegetables fix the carbon which enters into 

 by the simple moisture holding certain salts, the composition of this gas, and set the oxy- 

 &c. in solution, which is the food all vege- gen at liberty ; in the dark, however, a very 

 tables derive through their roots, be the effect different process goes forward ; they then 

 of vital elaboration within the cells of the actually absorb oxygen and exhale carbonic 

 woody fibre, or result from an admixture of the acid gas; the balance, however, in the aggre- 

 cambium or fluid which has already undergone gate is not equal between these opposite pro- 

 assimilation in the leaves, is still uncertain, cesses, a much larger quantity of carbon being 

 We are inclined to believe that a process ana- fixed by the decomposition of carbonic acid 

 logous to digestion does actually take place gas and oxygen set at liberty, than there is of 

 within the woody conduits of the sap of vege- oxygen absorbed and carbonic acid gas set free, 

 tables ; why should it not, or why should These acts are essential to the life and health 

 any new properties acquired by matters sub- of vegetables ; their end and object appear to 

 jected to the influence of the peculiar laws be the preparation of their proper nutritive 

 of vitality be held as resulting from mere ad- fluids or cambium : the sap which reached the 

 mixture ? leaves, colourless, not coagulable, without glo- 



The very same thing, in fact, happens among bules, mere water holding carbonic acid, 



the lowest tribes of animals which takes place acetic acid, a muco-saccharine matter, and 



in all vegetables : the substances fitted for their various salts in solution, is in them converted 



nourishment penetrate or are absorbed into into a greenish fluid, partly coagulable, and 



their systems, and are there assimilated without full of globules, which special vessels then 



the intermedium of any special apparatus, distribute for the growth and maintenance of 



We mount but a very short way in the scale the different parts. 



of the animal creation, however, before we The respiratory act is necessary, and goes on 



meet with a peculiar pouch, destined for the without the aid or concurrence of the indi- 



reception of the aliment, and accomplishment vidual among vegetables. 



of the first steps in the processes by which, in Animals are no less dependent than vege- 



the more perfect animals, it is finally assimi- tables on communication with the air of the 



lated. This pouch is the stomach, and with atmosphere, either immediately or mediately, 



the rest of the digestive apparatus with which for a continuance of their existence, or the 



it is connected, is in intimate and uniform re- manifestation of those acts whose sum con- 



lationship with the kind of food upon which stitutes their lives. In the very lowest tribes 



animals are led by their instincts to live. the communication between them and the air 



All the accessaries of the assimilating cavity of the atmosphere takes place over the surface 

 or stomach which we find in animals, from of the body generally, without the intennede 

 the organs of sense that guide them in their of any particular organ or organs for the pur- 

 choice of aliment, to the lips that seize it, the pose. The fluids absorbed into their bodies 

 teeth or jaws that bruise it or destroy its are brought into contact with the atmospheric 

 vitality, the muscular actions by which it is air in those points where they approach the 

 swallowed, and the chemico-vital processes by external surface, and there appear to undergo 

 which it is dissolved, and the purely vital sen- the changes necessary to fit them for being 

 sibilities by which such parts as are proper for converted into the substance of the animals 

 nourishment are retained, and such as are irn- themselves. Simple as this process may ap- 



