Hand-book of physiology / by W. Morrant Baker and Vincent Dormer Harris.

  • William Senhouse Kirkes
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: Hand-book of physiology / by W. Morrant Baker and Vincent Dormer Harris. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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    animals. It might at the outset of our inquiry have seemed an unnec- essary thing to recount the distinctions which exist between an animal and a vegetable as they are in many cases so obvious, but, however great the differences may be between the higher animals '-ind plants, in the lowest of them the distinctions are much less plain. In the first place, it is important to lay stress upon the differences between vegetable and animal cells, first as regards their structure and next as regards their functions. (].) It has been already mentioned that in animal cells an envelope or cell-wall is by no means always present. In adult vegetable cells, on the other hand, a well-defined cellulose wall is highly characteristic; this, it should be remembered, is non-nitrogenous, and thus differs' chemically as well as structurally from the contained protoplasmic mass. Moreover, in vegetable cells (fig. 17, b), the protoplasmic contents of the cell fall into two subdivisions: (1) a continuous film which lines the interior of the cellulose wall; and (2) a reticulate mass containing Fig. 17.—(a.) Young vegetable cells, showing cell-cavity entirely filled with granular protoplasm inclosing a large oval nucleus, with one or more nucleoli, (b.) Older cells from same plant, show- ing distinct cellulose-wall and vacuolation of protoplasm. the nucleus and occupying the cell cavity; its interstices are filled with fluid. In young vegetable cells such a distinction does not exist; a finely granular protoplasm occupies the whole cell-cavity (fig. 17, a). Another striking difference is the frequent presence of a large quan- tity of intercellular substance in animal tissues, while in vegetables it is comparatively rare, the requisite consistency being given to their tissues by the tough cellulose walls, often thickened by deposits of lignin. As an example of the manner in which this end is attained in animal tissues, may be mentioned the deposition of lime salts in a matrix of intercellular substance which occurs in the formation of bone. As regards the respective functions of animal and vegetable cells, one of the most important differences consists in the power which vege- table cells possess of being able to build up new complicated nitrogenous and non-nitrogenous bodies out of very simple chemical substances ob- tained from the air and from the soil. They obtain from the air, oxy- gen, carbonic anhydride, and water, as well as traces of ammonia gas; and from the soil they obtain water, ammonium salts, nitrates, sulphates,