HARVEY AND THE CIRCULATION. 243 



general circulation through similar channels, yet in 

 being distributed the capillaries will make of this 

 nutriment man, pig, dog, and cat, whether it go to 

 brain, gland, or muscle. Of course the digestive and 

 elaborative processes would exert an influence, yet the 

 capillaries impart the most potent influence. 



There are several lapses in the Harveian discovery 

 of the circulation of the blood, as far as at present 

 understood. The capillary circulation as one, the uses 

 of the pulmonary circulation as two, the causes of the 

 venous circulation as three, and the connection of the 

 lacteal and lymphatic vessels with the venous as four. 



The lapse in the capillary system has just been 

 described. That of the pulmonary circulation con- 

 sists in the fact that Harvey did not understand the 

 function of aeration. As has been said, he thought 

 the blood went to the luugs to be cooled, when in fact 

 that was only an accidental circumstance. The third 

 lapse is difficult to fully and satisfactorily explain. It 

 is known that the portal circulation is independent of 

 the heart's action or of any other visible propelling 

 cause. The capillaries of the portal vein gather the 

 blood from the chyle-making viscera, and after unit- 

 ing into one great venous trunk, pour it into the liver 

 through branches where it is again distributed as by a 

 heart and arteries, no display of force being percep- 

 tible in the collection or distribution. It may be easy 

 to say that the work is done by " capillary attraction," 

 yet that is not satisfactory to a logical mind. The 

 circulation in a tree from rootlets to leaves, may be by 

 kindred forces, yet it is not easy to state what they 

 are. Dr. Draper's idea that the sap is thickened in 

 the leaves, and then pushed along by the thinner fluid 

 which is constantly advancing is not satisfactory. 



