Page:Popular Science Monthly Volume 2.djvu/707

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oxygen of the globule is disengaged; combustion occurs with production of heat, but without flame, as is the case with starch; the blood becomes venous and darkish; then, sent back to the vessels of the lungs, it resumes its arterial coloring with the vital air.

In connection with the history of transfusion it is important to know the quantity of blood contained in the organism; this has been estimated, by approximation, and attempts have been made to ascertain it in the human subject. A criminal named Langguht was beheaded at Munich, July 7, 1855: about eleven pounds of blood were collected by Professor Bischoff. The weight of the body was one hundred and forty pounds; the proportion of blood being one thirteenth. This estimate has been accepted by many physiologists, although some believe it is too low. Nothing certain can be arrived at on the subject; does not the quantity of blood in our bodies vary according to very many conditions? It does not remain the same before and after eating, while asleep and while awake. In hibernating animals, as the marmot, or the dormouse, if the weight of the body decreases one-fourth in the period of rest, that of the blood is considerably reduced. The same fact is observed in fasting, the globules losing size and color. Disease produces a similar result, and nothing is more correct than the commonly-held opinion that "grief and privation consume the blood." The precise ideas we now have of the nature of this fluid have largely corrected Broussais's errors, and more than one practitioner in our day would assent to Galen's precept, that "in bleeding the measure of a half-pint must not be exceeded, and in any case the veins of a patient under fourteen must be spared." The study of transfusion proves the importance of the sanguine fluid better than any general considerations. We shall presently point out those well-settled cases in which the physician may practise the operation; but the reader is now prepared to understand how each part of the body derives supplies of life from contact with this fluid. The functions of the tissues will be briefly analyzed in turn; glands, muscles, nerves, spinal marrow, brain, will display their special activity. We shall see how the blood-globules feed singly all these flames, which blend and mingle to light the torch of life.

Secretion takes place by means of the glandular tissue. This function is connected with nutrition, and in the lower products of organized matter is identical with it. The simplest vegetables, and the lowest animals, are instances of this blending. In the higher degrees of animated beings, the elements of secretion separate and maintain their own life, finding in the surrounding air or the moistening fluids the conditions of their nourishment and work. In perfect organizations the glandular tissue becomes more complex, receiving nerves and vessels; natural transfusion of the blood begins to play an important part. The size and secreting energy of the glands are directly related to the quantity of blood passing through them; thus the kidneys, in-