I So BIOLOGY AND ITS MAKERS 



Among the ancient ])hysiologists the great Roman phy- 

 sician Cialen is the most noteworthy figure. As he was the 

 greatest anatomist, so he was also the greatest physiologist 

 of ancient times. All ])hysiological knowledge of the time 

 centered in his writings, and these were the standards of 

 physiology for many centuries, as they were also for anatomy. 

 In the early days anatomy, physiology, and medicine were all 

 united into a poorly digested mass of facts and fancies. This 

 state of affairs lasted until the sixteenth century, and then the 

 awakening came, through the efforts of gifted men, endued 

 with the spirit of independent investigation. The advances 

 made depended upon the work or leadership of these men, 

 and there are certain periods of especial importance for the 

 advance of physiology that must be pointed out. 



Period of Harvey. — The first of these epochs to be espe- 

 cially noted here is the period of Harvey (i 578-1657). In his 

 time the old idea of spirits and humiors was gi\ingway, but 

 there was still much vagueness regarding the activities of the 

 body. He helped to illuminate the subject by showing a con- 

 nection between arteries and veins, and by demonstrating 

 the circulation of the blood. As we have seen in an earlier 

 chapter, Harvey did not observe the blood passing through 

 the ca])illarics from arteries to veins, but his reasoning was 

 unassailable that such a connection must exist, and that the 

 blood made a complete circulation. He gave his conclusions 

 in his medical lectures as early as 1619, but did not publish 

 his views until 1628. It w^as reserved for Malpighi, in 1661, 

 actually to see the circulation through the capillaries under 

 the microscope, and for Leeuwenhoek, in 1669 and later 

 years, to extend these observations. 



It was during ?larvey's life that the microscope vras 

 brought into use and was of such great assistance in advanc- 

 ing knowledge. Harvey himself, however, made little use 

 of this instrument. It was during his life also that the knowl- 



