248 THE POPULAR SCIENCE MONTHLY 



ever, which preceded an adequate knowledge of biology in the form of 

 medical and sanitary knowledge, resulted in a high mortality rate, 

 which is always a heavy drain on society, and therefore a great impedi- 

 ment to progress. Not only was the ordinary death rate high, but oc- 

 casionally plagues swept over large areas making fearful havoc in the 

 population. Authorities state that the black death in the fourteenth 

 century took half the population of England. These pestilences were 

 spread by the increased travel and trade made possible by the very 

 progress which had been achieved in the control of nature. This period 

 of the predominance of the natural sciences may be called the great 

 period of natural selection. A denser population made possible by the 

 increasing control of nature was held in check by a high death rate, un- 

 controlled because of the lack of medical knowledge. But these un- 

 fortunate conditions resulting from the unequal advancement of knowl- 

 edge developed influences which were destined finally to reduce the 

 evils. Disease and death have always seemed great enough evils to 

 cause men to try to avoid them in more or less rational ways ; but in a 

 concentrated population these evils are brought forcibly to men's at- 

 tention especially when they come in the form of a disastrous pestilence. 

 Furthermore, increased association, which comes from a larger and 

 denser population, is the chief means of developing sympathy and of 

 arousing the desire to alleviate the sufferings of others. Hence the in- 

 creased sympathy for others, and the more vivid realization of the 

 amount of suffering in existence, became incentives for an increased 

 effort to lessen the evils of disease. Moreover, other altered conditions 

 caused these efforts to take a scientific turn. Previously superstitious 

 beliefs had hindered the progress of science. Plagues were considered 

 a visitation of the divine wrath, disease was treated with charms or 

 with appeals to the saints, and the growth of anatomical knowledge was 

 hindered by religious superstitions which forbade contact with dead 

 bodies. But the new knowledge of the material world gradually less- 

 ened the hold of these superstitions and prepared the way for the sci- 

 entific observation of the course of disease and the study of anatomy 

 by the laboratory method. 



In describing the effects of the natural sciences and the influences 

 which have caused the development of the biological sciences, I do not 

 mean to imply that the progress of knowledge has been continuous and 

 uninterrupted, so that one particular period of history may be pointed 

 out as having the conditions favorable for the origin of biology. There 

 are a number of periods in which the forces here mentioned have been 

 at work in greater or less degree and have influenced biological science. 

 Perhaps at no time have they been more in evidence than at present, 

 when, for example, modern conditions have turned people's attention 

 to the ravages of tuberculosis, and have increased efforts to overcome- 



