THE CONQUEST OF DISEASE 



Theevo- principles of physics. Humanity's debt of 

 lution of gratitude is incalculably great to those men 

 knowledge. who at the risk of their lives and fortunes made 



dissections of dead bodies of men and animals, 

 and discovered the mechanism of the muscular 

 system which imparts motion to the joints, the 

 valvular and pump-like arrangement of the 

 heart, and the hydraulic principles of the tubes 

 which convey the blood through the body. 

 Then came those students of the secrets of 

 nature who discovered that the same laws which 

 govern man govern the lower and the lowest of 

 creatures ; that between soil and mineral, fluids 

 and gases, plants and animals, there is no 

 dividing line ; that the lily is the daughter of the 

 pool, and man is the brother of the ox. This 

 knowledge was gotten for us, not by the philos- 

 opher among his books, but by the patient 

 investigator who went to the heart of nature 

 and studied her secrets. Out of these labors 

 grew the biologic sciences; and modern medi- 

 cine and hygiene were made possible. But 

 the cost has been very great to these in- 

 vestigators. Humanity has ever been unkind 

 to her greatest benefactors. From Andreas 

 Vesalius, the first of scientific anatomists, per- 

 secuted to death, having committed no greater 



