Page:Madras journal of literature and science vol 2 new series 1857.djvu/189

JULY — SEPT. 1857.] helween the Animal and Plant, 179 endesmose the elements of nutrition, which thus pass in their crude state into the general circulation, where they are elaborated and fitted for their future destiny. In the vertebrate animal, the lacteals already referred to terminate by looped extremities amongst a number of cells and nuclei; and during the passage of chyme along the intestine these nuclei become developed into cells, and the cells are busy at work selecting, absorbing and elaborating, and then yielding up their contents to the loops of the lacteals. In plants the root is the great organ of absorption, whether suspended in air, floating in water or buried in the earth. The root consists of a cellular epidermis, and internal structure of vascular bundles and cells. Here then cells are still the great organs of absorption, and if we trace the sap upwards through the alburnum and leaves, and its return through the lactiferous vessels and cells of the bark, we shall find them not less active and essential in the process of assimilation. If we now review the function of respiration in the animal and plant, we shall find that although by this process the animal eliminates carbon and consumes oxygen, while the plant fixes the former and gives off the latter, being thus so far opposed in object, they nevertheless agree inasmuch as respiration is carried on in both kingdoms, by means of organs of a cellular structure. In both too the ultimate objects of the function are the alteration and refinement of the circulating or nutritious fluid, the blood in the one and the sap in the other being fitted for the production of new or repair of old tissues, and for keeping up a supply of the various secretions. Respiration is therefore a depuratory process, and perhaps the least vital of any of the functions of organic life, many of the changes it effects being merely the results of a chemical action. We come now to speak of secretion, which is carried on by means of certain cellular organs called glands. These appropriate each a definite nature of material from the circulating fluid, as it passes along fertilized by the results of absorption and assimilation. Besides their nutritious elements however, the blood and sap contain unorganizable substances the effete products of tear and wear, which are separated to be excreted by glands differing in no important particulars from those already mentioned. The individual cells concerned in the manufacture of