Manual of comparative anatomy and physiology / by S. Messenger Bradley.

  • Samuel Messenger Bradley
Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: Manual of comparative anatomy and physiology / by S. Messenger Bradley. Source: Wellcome Collection.

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    blood, the chyle, &c. ; others become loaded with earthy or caL careous particles, and so build up the skeletons of animals ; others become converted into skin, by being flattened out and dried ; others, again, remain distinctly cellular, and constitute the animal secretions. There is very little difference between the individual vegetable and animal cell ; but the points to be chiefly noted are these. The vegetable cells are always perfect cells ; they are surrounded by very little blastema, they are mutually independent of each other, and they require for their nourishment a pabulum drawn from the inorganic world. On the other hand, animal cells are frequently imperfect^ being deficient in a cell wall ; they are always surrounded by a considerable amount of blastema, they are mutually dependent on each other, and they derive their nourishment from the organic world alone. By this latter pro- perty the two kingdoms supplement each other's requirements, and so maintain the natural cycle of life. The animal dies, and is resolved into the inorganic world, in which condition he be- comes food for the plant ; the plant then re-converts this pabulum into organic matter, when it re-becomes meet food for the animal. The dawn of animal life is, as may be gathered from what has gone before, indistinct, and often diflicult to discern. The border-land between the vegetable and animal kingdom is the scene of a perpetual conflict of opinion, doubtful forms changing sides more than once during the contest. Perhaps the most important diffierential characteristics of animals are, first, the fact of their food being always derived from the organic world, and, secondly, the fact that in their physiological processes they are synthetical, whilst vegetables are analytical; in other words, animals take in oxygen and give out carbonic acid, which is formed in their system ; whilst plants take in carbonic acid, and, breaking it up into its component parts, give out the oxygen and retain the carbon. Some fungi, however, require complex organisms for nourish- ment, and it is said, on the other hand, that the Protozoon called Bathybius, derives nourishment directly from the oxygen in the water. It follows from these facts that there is no single circumstance which separates the two kingdoms. The lowest plants and the lowest animals approach each other more closely than the high- est plants and the lowest animals, g,, the position of bacteria and vibriones is still doubtful, but no one could doubt the vegetable nature of any exogen, or the animal nature of any vertebrate. The lowest plants and animals seem indeed to meet b2
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