to the action of neighbouring cilia. A corpuscle will sometimes as- sume the figure of an hour-glass, as if it were preparing to divide itself into two parts, but it instantaneously either regains its previ- ous form, or assumes a new one. These motions are incessant, and so rapid that it is not easy to catch and delineate any of the result- ing forms ; they are compared to the writhings of an animal in pain. The author has seen them in a rabbit, as late as two hours and a half after death, and thinks it probable that they may continue for a longer time, although, when under the microscope, they gradually and in a short time cease ; the rapid changes of form, which are at first apparent, passing into gentle undulations, and being succeeded by an alternation of rest and motion.
Should these facts be thought to confirm the opinion of John Hunter, that the blood "has life within itself," or " acquires it in the act of forming organic bodies," because its corpuscles in certain states exhibit " vital actions," still his assertion that " the red glo- bules" are the least important part of the blood, will appear to have no just foundation.
The author finds that the phenomena attending what is called " vital turgescence" of the blood-vessels, depend not merely on an accumulation and stagnation of blood, but on changes in the condi- tion of its corpuscles, which assume a more or less globular, or ellip- tical appearance resembling cells. Their interior is dark, from a great increase of red colouring matter which accumulates around a pellucid and colourless point, corresponding in situation to that of the central part of nuclei in other cases ; and so completely do the corpuscles fill their vessels, that the fluid portion of the blood is ex- cluded, and the corpuscles are compressed into polyhedral forms. This condition of the blood- corpuscles during vital turgescence of the vessels, the author thinks deserving of consideration, in connexion vdth. many of the phenomena attending local accumulations of blood, both in health and in disease ; and more especially with reference to increased pulsation, the exudation of colourless fluid, and the heat and redness of inflamed parts.
According to the views of the author, the formation and nourish- ment of organs is not effected merely by the fluid portion of the blood, for he has discovered that the cells which he showed in his " Third Series of Researches in Embryology" form the chorion, are altered blood- corpuscles ; and he has farther found that muscular fibre (that is, the future muscle -cylinder, not the fibril) is formed by the coalescence of cells, which also are derived from corpuscles of the blood. He has seen and figured every stage of transition, from the unaltered blood-corpuscle to the branched cells forming the chorion, on the one hand, and to the elliptical or oblong muscle-cells, on the other. The colour is not changed, except that the blood-corpuscles, when passing into cells for the formation of muscle, become of a much deeper red. There seems to occur in these an increase of red colouring matter.
Valentin, in describing the mode of the formation of muscle, had stated that globules approach one another and coalesce to form
