Page:General History of Europe 1921.djvu/794

594 General History of Europe a mistake. The cell corresponds, in a way, to the molecules which form inanimate substances. 1 The cell theory underlies the study of biology and is shedding a flood of light upon the manner in which the original cell, or egg, from which all animals come, develops and gradually gives rise to all the tissues and organs of the body. It has helped to explain many diseases and in some cases to suggest remedies, or at least rational methods of treatment. The human body and the func- tions of its various organs and their relations to one another, the extraordinary activities of the blood corpuscles, the nerves and their head and master the brain, all these subjects and many others have been studied in the ever-increasing number of labora- tories and well-equipped hospitals which have been founded dur- ing the past century. It is clear enough, in the light of our present knowledge, that the physicians of former days relied upon drugs and other treatment which were often far worse than nothing. 1080. Some Marvels in Medicine. In 1796 Edward Jenner first ventured to try vaccination and thus found a means of prevention for one of the most terrible diseases of his time. With the precautions which experience has taught, his discovery would doubtless rid the world of smallpox altogether if vaccination could be everywhere enforced. But there are always great numbers of negligent persons as well as some actual opponents of vaccination who will combine to give the disease, happily much diminished in prevalence, a long lease of life. 1081. Use of Anaesthetics introduced (i840-i85o). Some fifty years after Jenner's first epoch-making experiment, operations began to be made on patients who had been rendered unconscious by the use of an anaesthetic ; namely, ether. Chloroform soon 1 Many very low organisms, like the bacteria, consist of a single cell. The human body, on the other hand, is estimated to contain over twenty-six billions of cells, that is, of minute masses of protoplasm, each of which is due to the division of a previous cell, and all of which sprang from a single original cell, called the ovum, or egg. " All these cells are not alike, however, but just as in a social community one group of individuals devotes itself to the performance of one of the duties requisite to the well-being of the community and another group devotes itself to the performance of another duty, so too, in the body, one group of cells takes upon itself one special function and another, another" (McMurrich, The Development of the Human Body (1907), p. 2).