There are but few acids which exist in the vegetable and animal kingdoms in common ; and whilst their number is small among ani mals, it is very great among vegetables.
The hydrocyanic acid has only been dis covered in vegetables; when it is procured from animal substances, it is always formed un der peculiar circumstances, or during their de corn position .
Of the organic oxides, some—albumen, osma zonie, sugar—are common to both animals and vegetables ; but they occur in very different proportions in each : sugar, which is so abundant among plants, is scarcely to be detected among animals ; and osmazome, which is so univer sally distributed among animals, has only hitherto been discovered in a few fungi. Of the ternary compounds of carbon, hydrogen, and oxy gen; such as starch, gam, sugar, the re.sins,woody fibre, fixed oils, volat ile oils, camphor, extractive inutter,4c. which enter so largely into the consti tution of vegetables, there are but a very few to be discovered among animals, such as the sugar of the milk and urine, the resin of the bile and of the urine, the elaine and stearine of the fat, the volatile oily principle of castoreum, &c. and the camphor of cantharides.
The quaternary organic compounds of car bon, hydrogen, oxygen, and nitrogen, which form the principal elements in the composition of the bodies of animals, are, on the contrary, very rare among vegetables. The most com mon of these are albumen, gelatine, fibrine, animal mucus, and osmazome ; the less com mon enumerated are the matter of the saliva, caseous matter, urea, and the pigmentary mat ter of the eye.
Still vegetables are not without several of these quaternary compolinds, such as albumen and osmazome and they even possess others which are peculiar to themselves, such as gluten, the matter of the pollen of flowers, indigo and several extractive colouring principles ; to say nothing of the whole exclusive class of salifiable bases, quinia, cinchonia, veratria, strychnia, morphia, &c., &c., which appear to be corn pounds of carbon, united in large proportion with a little oxygen, hydrogen, and nitrogen.
Comparison qf the "organic composition or texture of annuals and vegetables.—We find many and much more striking differences in the texture than in the chemical composition of the two great classes of organized beings. Both are made up of solids and fluids ; but with a few exceptions, the proportion which the solid bear to the fluid parts is much greater in vegetables than in animals.
The fluids' contained in the bodies of the higher animals, the blood, chyle, spermatic fluid, bile, urine, &c. have in general a very. different character from those that constitute the sap of the more perfect vegetables, or that are deposited as secretions in the sectaries and various cavities of their flowers, leaf-stalks, stem, &c. • But the solids, entering into the composition of each class, are still more widely dissimilar both in their outward and in their intimate characters. The most simple vegetables, the cryptogamia, appear to consist of a homo geneous tissue, forming rounded or oblong cells filled with fluids or a granular substance, with out any trace of proper tissue ; it is only when we come to the phanogamous vegeta bles that we find any distinction of tissues, namely, a cellular and a tubular tissue, the whole body of the plant being surrounded with a distinct integument or bark.
The cellular tissue of vegetables, whilst still young, is soft, homogeneous, and contains cellules filled with a fluid often charged with globules ; when full grown, this tissue is made up of cells properly so called, being spaces surrounded with solid membranous parietes of various forms and sizes containing different matters. These cells appear composed of vesi cles placed side by side and running one into another, surrounding the spiral and nutrient vessels of the stern and bark, arid opening so as to form reservoirs filled with air, or resinous, oily, or mucilaginous fluids.
The tubular or vascular tissue of vegetables occurs under two different forms—spiral vessels, and nutrient vessels. The former present themselves in great abundance amidst the woody fibres, but penetrate also into the leaves, and even into the stamina, pistilla, and fruit. They are not met with in the bark. These vessels seem specially destined to include and conduct the sap, which from the root ascends to the extreme branches and leaves of all vege tables. The nutrient vessels, so called from con taining a fluid, the cambium or succus proprius, different from the sap, prepared from this by elaboration in the leaves, have now been demon strated in a great number of vegetables; they are principally contained in the soft inner layer of the bark, but they also penetrate every part for the purpose of conveying the essentially nutritive juice or blood of the plant.