Like a bellows the lungs fanned and cooled this vital blood.

Here and there we find glimmering conceptions of a communication between these systems, but practically all teachers believed that the only one of importance was through small pores in the wall separating the two sides of the heart.

Observation--merely looking at and thinking about things--had done all that was possible, and further progress had to await the introduction of a new method, viz., experiment.

Galen, it is true, had used this means to show that the arteries of the body contained blood and not air.

The day had come when men were no longer content with accurate description and with finely spun theories and dreams.