Circulation of the Blood 151 



moves more slowly through narrower channels ; it is 

 more effectually strained in its passage through the 

 substance of the liver than through that of the lungs. 

 It has not the same velocity through flesh and the 

 softer parenchymatous structures and through sinewy 

 parts of greater compactness and consistency : for the 

 thinner and purer and more spirituous part permeates 

 more quickly, the thicker more earthy and indifferently 

 concocted portion moves more slowly, or is refused 

 admission. The nutritive portion, or ultimate aliment 

 of the tissues, the dew or cambium, is of a more pene- 

 trating nature, inasmuch as it has to be added every- 

 where, and to everything that grows and is nourished 

 in its length and thickness, even to the horns, nails, 

 hair, and feathers ; and then the excrementitious 

 matters have to be secreted in some places, where 

 they accumulate, and either prove a burthen or are 

 concocted. But I do not imagine that the excremen- 

 titious fluids or bad humours when once separated, nor 

 the milk, the phlegm, and the spermatic fluid, nor the 

 ultimate nutritive part, the dew or cambium, necessarily 

 circulate with the blood : that which nourishes every 

 part adheres and becomes agglutinated to it. Upon 

 each of these topics and various others besides, to be 

 discussed and demonstrated in their several places, viz. 

 in the physiology and other parts of the art of medicine, 

 as well as of the consequences, advantages or dis- 

 advantages of the circulation of the blood, I do not 

 mean to touch here ; it were fruitless indeed to do so 

 until the circulation has been established and conceded 

 as a fact. And here the example of astronomy is by 

 no means to be followed, in which from mere appear- 

 ances or phenomena that which is in fact, and the 

 reason wherefore it is so, are investigated. But as 

 he who inquires into the cause of an eclipse must 

 be placed beyond the moon if he would ascertain it 

 by sense, and not by reason, still in reference to things 

 sensible, things that come under the cognizance of the 



