COMPARISON OF ANIMALS AND VEGETABLES.
Animals and vegetables were longheld essenti ally and irreconcilably distinct from one another. We have already had occasion, however, to observe in hoW many particulars they are iden tical. The material composition of both is often in opposition with the general physico-chemical laws, both are made up of a combination of solids and fluids, both consist of a variety of heterogeneous parts, and both have determinate sizes which they cannot exceed. Moreover, both are possessed of vitalay,—in other words, both commence by a genesis, preserve them selves as individuals by nutrition, and as spe cies by reproduction ; both grow by intus-sus ception, undergo the mutations which are denominated ages, endure for a time, present themselves in health or labouring under disease, and both decay and die., How intimately ani mals and vegetables are associated, how nearly they resemble one another, will farther appear as we advance in the following Comparison the general physical qualities and material composition of Vegetables and Animals.—As a general axiom the material constitution of vegetables may be said to be less complex than that of animals; this at least is more especially the case as the individuals at the top of the two scales are concerned.
No distinguishing feature of either class is derivable from general diversity of Size. Be tween the microscopic lichen and infusory ani mal, and the gigantic adansonia and whale, plants and animals of every intermediate mag nitude are encountered.
Neither is there much to be said upon the differences which vegetables and animals pre sent when their Forms are contrasted. The forms of many are alike amorphous, or simply globular ; certain pulverulent fungi in the one class, and monads in the other, resemble each other greatly. Among both, individuals also occur whose parts are disposed around a centre; yet we do not advance far before we discover a peculiarity in animals, namely, composition by the union of two similar or symmetrical halves along a middle line or axis, nothing similar to which has even been imagined in the vegetable world, the members of which on the contrary often exhibit a horizontal division, but without anything of symmetry, into root and branches.
As a general law the animal kingdom may be said to affect the globular or simply produced form, with radii in the shape of extremities sent off from a central part; the vegetable to exhibit a greater tendency to ramification or division into branches.
In point of chemical composition animals and vegetables consist very nearly of the same elements: oxygen, hydrogen, carbon, nitrogen, phosphorus, sulphur, iodine, bro mine, chlorine, potassium, sodium, calcium, silicium, magnesium, manganese, and iron have been detected in both ; aluminium and copper have hitherto only been discovered in vegetables, and fluor only in animals. But these elements are united in each in very dif ferent relative proportions. Carbon predomi nates greatly in the more solid parts of vege tables, nitrogen in the bodies of animals gene rally,althougli to this rule there are many notable exceptions ; albumen, fibrine, and gelatine all contain much more carbon than nitrogen, and certain fungi include a very large proportion of nitrogen in their composition. Several ele ments, met with abundantly in animals, occur but sparingly distributed among vegetables, phosphorus, for example, and sulphur. The earth afforded by animal bodies incinerated, is mostly lime in a state of saline combination ; whilst that yielded by Vegetables, besides lime, consists of alumina, with an admixture, greater or smaller in amount, of scilica.
The peculiar combinations which form what are called immediate principles, are much more numerous in the vegetable than in the animal kingdom, and are also generally more simple in the former than in the latter, the immediate principles of vegetables being mostly ternary compounds, whilst those of animals are gene rally quaternary, nitrogen being added in these last to the carbon, hydrogen, and oxygen, which form the organic elements of the first. The immediate principles in both classes are divided into acids and oxides ; and many of these they have in common. Vegetables, however, have a third order of substances entering into their composition, of which we discover no traces among animals ; these are the vegetable sali liable bases.