Mercers' Company lectures on the fluids of the body.

  • Ernest Starling
Date:
1909
Catalogue details

Licence: In copyright

Credit: Mercers' Company lectures on the fluids of the body. 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.

    47/204 (page 35)
    In i3lant cells, with their firm cellulose walls, small changes in the molecular concentration of the smTonnding medium need not cause an}^ ill effects, apart from temporary modifi- cations in the condition of turgor. Animal cells, on the other hand, must be extremely susceptible to any such changes. The varying concentration of the medium in which they are immersed must bring about a continual and corre- sponding variation in size and content in water of the cell. Moreover, their protoplasm is directly exposed to the influence of the slight qualitative changes in the environment which, as we have seen, exert such wide-reaching influences on all the cell functions. A great step in evolution was taken therefore, when the organism secured for the majority of its cells a medium of uniform composition, by the formation of a body-cavity or coelom, and the enclosing in this cavity of a fluid not differing widely at first from the surrounding sea-water. This step was typical of the whole course of the evolution which results in rise of type. Even at the present time the position of a man among his fellows, or of a man among other animals, is indicated by the extent to which he is able to create his environment and to keep it adapted to his special needs, so that he may never experience directly tJie numerous adverse influences which are present just outside his own self-created circle. Every slight deviation of an ocean current, every spell of cold weather, brings about the sacrifice of myriads of living beings, which are unable to withstand the trifling changes of saline concentration or temperature thereby in- duced in their surroundings. The evolution of a coelom was followed by the appearance of circulatory and other organs designed to maintain the composition of the internal medium constant at all parts of the organism under varying internal conditions. In the highest vertebrata, the evolution of a D 2