12 PATHFINDERS OF PHYSIOLOGY 



the blood into the pulmonary arteries, the pulsations of which were 

 simultaneous with the other arteries of the body. He demonstrated 

 that the two ventricles contracted simultaneously and that the two 



,/ auricles contracted at the same time. 



iJ 



AT Motion, Action and Office of the Heart. — In the fifth chapter 



^V^^;^arvey deals with the motion and function of the heart. It j:fiad*j- 



j^y somewhat like a modernjwprkjn physiology. 



/ "First of all, the auricle contracts, and in the course of its contraction 



throws the blood (which it contains in ample quantity as the head of the veins, 

 the storehouse, and cistern of the blood), into the ventricle, which, being filled, 

 the heart raises itself straightway, makes all, its fibres tense, contracts the ven- 

 tricles, and performs a beat, by which beat it immediately sends the blood sup- 

 plied to it by the auricle into the arteries; the right ventricle sending its charge 

 into the lungs by the vessel which is called vena-arteriosa, but which, in structure 

 and function, and all things else, is an artery; the left ventricle sending its 

 charge into the aorta, and through this by the arteries to the body at large. 

 These two motions, one of the ventricles, another of the auricles, take plpce con- 

 secutively, but in such a manner that there is a kind of harmony or rhythm pre- 

 served between them, the two concurring in such wise that but one motion is 

 apparent, especially' in the warmer blooded animals, in which the movements in 

 question are rapid." 



So far as Harvey's reasoning is based upon his observations his 

 conclusions are in the main correct, as proved by more recent re- 

 search ; where he indulges in speculation we get the following : 



"In the larger and more perfect animals of mature age Nature 

 has rather chosen to make the blood percolate the parenchyma of the 

 lungs. * * * It must be because the larger and more perfect animals 

 are warmer, and when adult their heat greater, ignited I may say 

 and requiring to be damped or mitigated, that the blood is sent 

 through the lungs, in order that it may be tempered by the air that 

 is inspired and prevented from boiling up and so becoming extin- 

 guished or something else of the sort," or, to modernize it, the lungs 

 serve as radiator and the heart the gasoline or internal^ combustion 

 engine. /^"^^^ 



Capillary Circulation. — Since Harvey's time Malpighi, in 1661, 

 hinted at the capillary circulation, which was still further investi- 

 gated by Leuwenhoek in 1674, who studied it with his microscope in 

 the web of a frog's foot and in other transparent membranes. In 

 1676, Blankaart, and in 1697 Cowper, studied the arrangement of the 

 capillaries by means of injected specimens. A long interval elapsed 

 between the histological study of the circulation before chemistry 

 was sufficiently advanced to afford definite knowledge in regard to 

 oxidation of the blood and the explanation of the true function of 

 the lungs. The work of Priestly in 1775 was a notable contribution 

 to the physiology of respiration. The nineteenth century, through 

 the work of Ludwig in Germany, Chauveau in France, and Foster in 

 England, has seen the physics of the heart and circulation reduced 

 almost to an exact science. - ) 



Any account of the works of Harvey would be incomplete were 

 no mention made of his work in embryology. Harvey discussed the 

 nature of development and exhibited extraordinary powers as re- 



