BIOLOGY IN HUMAN AFFAIRS 



In the meantime biology had set another milestone in its 

 course. William Harvey (1578-1667) had demonstrated the 

 circulation of the blood, and thus had laid a foundation 

 for the quantitative study of physiological processes. 

 Without the aid of the microscope Harvey was unable to 

 trace the capillaries and to interpret their function, this 

 discovery falling to the lot of Malpighi six years before 

 Harvey's death. But Harvey did something better. He used 

 his reasoning power. By observing carefully the action 

 of the heart and the difference in structure of the veins and 

 the arteries, he was able to show definitely that the 

 quantity of blood pumped into the aorta in a given time 

 makes its return to the heart necessary, since in less than 

 half an hour a quantity of blood greater than that con- 

 tained in the whole body passes into the great artery. The 

 consequences of this discovery were epoch-making, in that 

 it was fundamental to a true idea of respiration and hence 

 to the proper conception of the body chemistry. But it 

 was more than this. It showed that biology could pass 

 beyond the mere classificatory stage and begin to compare 

 relationships between observed phenomena. 



During the latter part of the seventeenth century, the 

 whole of the eighteenth century, and the first quarter of the 

 nineteenth century, biology was by no means stationary. 

 An enormous quantity of carefully collated observations 

 were given to the public. Life histories of thousands of 

 organisms were completed. The organic world was en- 

 larged by the discovery of protozoa and bacteria. Botany 

 flourished. Linnaeus put the classification of animals and 

 plants on a sounder and more satisfactory basis. Lamarck 

 endeavored to demonstrate organic evolution. Neverthe- 

 less, biology had not learned to walk, or to run, as it does 

 at the present day; it still crept. Its progress was so slow 

 that if one takes the total biological knowledge of to-day — 

 weighted in proportion .to its importance — as one hundred, 



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