Principles of comparative physiology / by William B. Carpenter.

  • William Benjamin Carpenter
Date:
1854
Catalogue details

Licence: Public Domain Mark

Credit: Principles of comparative physiology / by William B. Carpenter. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    156/810 (page 122)
    the Animal Kingdom; but as a third element (the senson-motor appara- tus) here comes into operation, it is not always so apparent. It appears to be a universal principle, however, that diuing the period of rapid growth, when all the energies of the system are concentrated upon the ]jerfection of its individual stmcture, the reproductive system remains dormant, and is not aroused until the diminished activity of the nntritive functions allows it to be exercised without injury to them. Thiis, in the Larva condition of the Insect, the assimilation of food and the increase of its bulk seem the sole objects of its existence; its loco- motive powers are only adapted to obtain nourishment that is within easy reach, to which it is directed by the position of its egg, and by an unerring instinct that seems to have no other end. The same is the case, more or less, with all young animals j although there are few in which voracity is so predominant a characteristic. In the Imago, or perfect Insect, on the other hand, the fulfilment of the purposes of its generative system appears to be the chief and often the only end of its being. The increased locomotive powers which are conferi-ed upon it, are evidently designed to enable it to seek its mate; its instinct appears to direct it to this object, as before to the acquisition of food; it now shuns the aliment it previously devoured with avidity, and frequently dies as soon as the foundation is laid for a new generation, without having taken any nutri- ment from the period of its fii'st metamoiT[5hosis. In the adult condition of the higher Animals, again, it is always found that, as in Plants, an excessive activity of the nutritive functions indisposes the system to the performance of the reproductive; a moderately-fed population multiply- ing (cseteris paribus) more rapidly than one habituated to a plethoric condition. 93. On analysing the operations which take place in the Animal body, we find that a large number of them are of essentially the same character with the foregoing, and difier only in the conditions under which they are performed; so that we may, in fact, readily separate the Organic fimc- tions, which are directly concerned in the development and maintenance of the fabric, from the Animal functions, which render the individual conscious of external impressions, and capable of executing spontaneous movements. The relative development of the organs destined to these two purposes, differs considerably in the several groups of Animals, as we have already in part seen (chap, i.) The life of a Zoophyte is upon the whole much more 'vegetative' than ' animal'; and we perceive m it, not merely the very feeble development of those powers which are pecidiar to the Animal kingdom, but also that tendency to indefimte extension which is characteristic of the Plant. In the perfect Insect, we have the opposite extreme; the most active powers of motion, and sensations oi which some (at least) are very acute, being combined with a low deve- lopment of the organs of nutrition. In Man and his allies we have less active powers of locomotion, but a much greater variety of Animal facili- ties- whilst the instilments of the organic or nutiitive operations attain theii' highest development, and their greatest degree of mutual depend- ence We see in the fabric of all beings m which the Animal powei-s are much developed, an almost entire want of that tendency to indefimte SensTon wMch is so characteristic of the Plant; and when the large :lrt oftod consumed by them is considered, the question naturally