Outlines of comparative physiology : touching the structure and development of the races of animals, living and extinct / by Louis Agassiz and A.A. Gould.

Date:
1851
Catalogue details

Licence: Public Domain Mark

Credit: Outlines of comparative physiology : touching the structure and development of the races of animals, living and extinct / by Louis Agassiz and A.A. Gould. Source: Wellcome Collection.

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

    50/508 page 20
    organic parts enlarge, as is distinctly seen in the cells of the epithelium, in the muscular fibres, and in the primary fibrous fasciculi of the nerves ; whilst mere nuclei, as the blood, lymph, or pus-globule, remain, or suffer diminution in the course of farther development.]* SECTION III. DIFFERENCES BETWEEN ANIMALS AND PLANTS. § 57. At first sight, nothing would appear more widely different than animals and plants. What is there in common, for instance, between an oak and the bird which seeks shelter amidst its foliage ? § 58. The difference, indeed, is usually so obvious, that the question would be superfluous, if applied only to the higher forms of the two kingdoms ; but as we descend to the simpler and therefore lower forms, the distinctions become so few, and so feebly characterized, that it is at length difiicult to pronounce whether the object we have before us is an animal or a plant. Thus, the sponges have so great a resemblance to some polyps, that they have generally been included in the animal, although in reality they belong to the vegetable kingdom.f § 59. Animals and plants differ in the relative predomi- nance of their component elements, oxygen, carbon, hydrogen, and nitrogen. In vegetables, only a small proportion of nitro- gen is found, while this element enters largely into the com- position of animal tissues. § 60. Another pecuharity of the animal kingdom is the presence of large, distinctly limited cavities, for the lodgment of certain organs; such is the skull and the chest in the higher animals, the branchial chamber in fishes, and the abdomen or general cavity of the body, which exists in all animals, with- out exception, for the reception of the digestive organs. § 61. The well-defined and compact forms of the organs lodged in these cavities is a peculiarity belonging to animals only. In plants, the organs designed for special purposes are never embodied into one mass, but are distributed over various parts of the individual; thus the leaves, which ausv»^er to the * Wagner’s Physiology, p. 221. f The animality of sponges is maintained hy some of oui' most dis- tinguished naturalists.—Ed.
    digitised image 1
    digitised image 2
    digitised image 3