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    microscopes , to consist of distinct red particles ; in man , of a circular form , flattened or slightly concave at each side , variously estimated in size from the -g ^ ^ to the - $ < hjv of an inch . The particles are per * fectly transparent , and are seen to have a disposition to arrange themselves into piles , and the motion amongst them in producing this arrangement seems to depend on vitality , for it becomes more feeble

    the longer they have been removed from the body . In the mammalia they are always circular ; in birds , reptiles , and fishes , elliptical ; and they are larger in the fish than in any other creature . The least addition of pure water makes them assume a globular form , but any salt prevents this alteration . It is not known in what part of the system they are formed , but Dr . Smith observed the uniformity of their figure and size in each species of animals ; and the undeviating precision with which they assume an elongated figure in oviparous and a circular figure in viviparous animals , leads to the supposition that their formation is owing to some simple but very powerful cause . ' The fluid portion of the blood is called the serum . It is a transparent fluid of a light straw colour , with a saline taste . By certain chemical agents and by heat , it is converted into a white substance , exactly like white of egg ; it is , in fact , pure albumen . A thin fluid

    drains from it , called the serosity of the blood . This is the fluid which , when it issues from meat , is called gravy . The strongest and most ferocious animals have the smallest proportion of serum ; and its quantity is considerably altered in disease ; in severe typhus fever it is much increased : it is the fluid which is poured into the different cavities in dropsy . It contains a quantity of uncombined alkali , and holds in solution various earthy substances and neutral salts .

    The component parts of the blood then are first , the hahtus ; second , the clot , composed of fibrin and red particles ; third , the serum , composed of albumen and serosity . The vital properties of the blood are yet to be explained , for the 4 > lood Is alive . The proofs of this fact are various and convincing . 1 . It is capable , like other living substances , of resisting within a wide range , the influence of physical agents . The egg while fresh is alive .

    During the period of incubation a hen ' s egg is kept for three weeks at a temperature of 103 ° , yet when the chick is hatched the yolk is found perfectly sweet ; but if the life of the egg be destroyed by passing the electric fluid through it , and if it be then exposed to this degree of heat , it putrifies with the same rapidity as other dead animal matter . A living egg exposed to the 17 th and 15 th degrees of Fahrenheit took half an hour to freeze ; when thawed and exposed

    only to 25 ° , it was frozen in a quarter of an hour . A living egg and one which had been frozen and thawed were placed together in a freezing mixture at 15 ° ; the dead egg was frozen 25 ' sooner than the other . Exactly the same results were obtained by analogous experiments upon the blood . It was found that a much shorter time and a much less degree of cold were required to freeze blood that had been previously frozen and thawed , than blood that had recently been taken from its vessel .

    2 . Blood has the power of becoming organized . Just as in the living egg when exposed to a certain degree of heat , certain motions spontaneously arise which end in the developement of the chick , so if

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    Dr . Southwood Smith on the Animal Economy . 123

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    K 2

• Citation
  • Monthly Repository (1806-1838) and Unitarian Chronicle (1832-1833), Feb. 2, 1833, page 123, in the Nineteenth-Century Serials Edition (2008; 2018) ncse.ac.uk/periodicals/mruc/issues/vm2-ncseproduct2608/page/55/