A practical treatise on the diseases of children / by James Stewart.

  • Stewart, James, 1799-1864
Date:
1841
Catalogue details

Licence: Public Domain Mark

Credit: A practical treatise on the diseases of children / by James Stewart. Source: Wellcome Collection.

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    The young animal, unlike his after mode of existence, obtains his nourishment by absorption, or transmission of the appropriate sti- muli for developement and support. Plants may be produced by offsets or cuttings: in the lower animals, zoophytes and polypes, propagation is effected in the same manner. Growth and nourish- ment are here produced by the inherent vitality of the separated slip or portion of the plant or animal, entirely distinct from any supposed centre of vitality which exists in the germ or matured structure; the principle of developement being excited into activity by the influence of heat, moisture, and perhaps other causes; of which, in our present state of knowledge, we have but a very imper- fect idea. Plants, like animals, possess a circulating system; arteries and veins, sap vessels or lacteals, and lymphatics. The arteries arise from the root, and convey nourishment upwards ; next to these are the veins, which return the elaborated sap from the leaves to the new layer of the liber.* The sap vessels, corresponding to the lacteals in animals, convey the nourishment to the body of the plant as the chylous vessels do from the intestines of the animal. The lymphatics of the plant are found immediately beneath the cu- ticle, and from the direction of the valves appear to be intended to pass the fluid in the same direction as the veins. Plants, then, have a double circulation ; the arteries and lacteals to convey the sap up- ward, the veins and lymphatics to pass it in the opposite direc- tion.| Plants also possess, equally with animals, vessels for cuta- neous transpiration. Some of them, as the sunflower, Helianthus annuus, give out an enormous quantity of perspirable fluid com- pared with their bulk. . A compound fluid exists in vegetables, corresponding to the blood in animals; and as the secretion of substances possessing various qualities, from that of a simple article of nourishment to one highly destructive to animal life, occurs in the same plant, so does the blood separate in animals, as in some of the reptile tribe, secretions for nourishment, and a poisonous juice, destructive to the life of animals, for defence. Respiration is a process which is continually taking place in » plants as well asin animals: and, in the fungi, almost as actively as in animals. * Smith’s Introduction to Botany, p. 56, et. seq. t Wildenow’s Introduction, p, 236,
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