638 THE POPULAR SCIENCE MONTHLY. 



has come very gradually. At first the student of medicine enlarged 

 his field of study, from disease and its phenomena, until it included the 

 structure and action of tissues and organs in health. Physiology and 

 anatomy, of little importance in the old science of medicine, began to 

 have recognized value. After this it was found that organs did not 

 always become disordered because of assaults from within the body, 

 but that they were affected by external influences. 



It was found that the organs must not only preserve equilibrium 

 within the body, but that there must also be equilibrium between the 

 body and its externals. It was discovered that in every organ there 

 were forces that built up and forces that pulled down, and that out- 

 side of it there were also conservative and destructive forces, and it 

 became obvious that, unless these acted so as to preserve equilibrium, 

 disease, and finally death, must ensue. Thus the art of healing and 

 the science of medicine are now very far from being as simple as they 

 were a century ago, and every year adds to their complexity. The 

 physician of to-day must have full knowledge of man as man, of anat- 

 omy and physiology, as a necessary foundation upon which his further 

 studies must rest. 



Physiology especially has developed during the last fifty years, so 

 that it has almost become a science by itself, but it still remains a part 

 of the wider science of biology. Here again we see a difference be- 

 tween the studies of the ancient and modern physician. To-day, and 

 still more in the near future, the physician must extend his studies be- 

 yond man, and the reason is plain. Man, with whom alone the physician 

 formerly supposed himself concerned, is but an isolated being discon- 

 nected from the rest of nature. Nature tolerates no such isolation. 

 No living being, even the simplest, exists, or can exist, independently 

 of other beings. It affects them and is affected by them, and what is 

 true of the simplest is yet more true of the more complex and most of 

 all of man. Nature is one, and all her creatures are parts of the whole. 

 For this reason man can not be fully known merely as man, he must 

 also be known as a part of the animal kingdom. No one can well un- 

 derstand human anatomy or physiology who knows nothing of that of 

 the lower animals. Comparative anatomy and physiology have thrown 

 very much light upon many obscure problems to which the study of 

 man gave rise. Therefore, I would most earnestly urge upon all med- 

 ical men the study of biology. It may be replied that the courses of 

 study are now crowded, but it is certain that the successful physician 

 of the future must know something of nature as a whole. Already 

 many of our most important theories as to disease the structure of 

 organs, cell-growth, cell-life, and many more have come to medicine 

 from biology. In an address before the International Medical Con- 

 gress held in London in August, 1881, Professor Huxley remarks that 

 " the search for the explanation of diseased states in modified cell-life, 

 the discovery of the important part played by parasitic organisms in 



