XV] OF BLOOD-VESSELS 955 



superable difficulties" of this sort of problem*. Some other 

 explanation must be sought in order to account for a phenomenon 

 which particularly impressed John Hunter's mind, namely the 

 gradually altering angle at which the successive intercostal arteries 

 are given off from the thoracic aorta: the special interest of this 

 case arising from the regularity and symmetry of the series, for 

 "there is not another set of arteries in the body whose origins are 

 so much the same, whose offices are so much the same, whose dis- 

 tances from their origin.to the place of use, and whose uses [? sizes] f 

 are so much the same." 



The mechanical and hydrodynamical aspect of the circulation 

 was as plain to John Hunter's mind as it had been to William 

 Harvey or to Stephen Hales, or as it was" afterwards to Thomas 

 Young; but it was not always plain to other men. When a turtle's 

 heart has been removed from its body, the blood may still be seen 

 moving in the capillaries for some short while thereafter; and 

 Haller, seeing this, "attributed it to some unknown power which 

 he conceived to be exerted by the solid tissues on the blood and also 

 by the globules of the blood on each other; to which power, until 

 further investigation should elucidate its nature, he gave the name 

 of attraction'' So said WilHam Sharpey, the father of modern 

 Enghsh physiology; and Sharpey went on to say that "many 

 physiologists accordingly maintain the existence of a peculiar pro- 

 pulsive power in the coats of the capillary vessels different from 

 contractility, or that the globules of the blood are possessed of the 

 power of spontaneous motion." Alison, great physician and famous 

 vitalist, "extended this view, in so far as he regards the motion 

 of the blood in the capillaries as one of the effects produced by what 

 he calls vital attraction and repulsion, powers which he conceives 

 to be general attributes of hving matter." But Sharpey 's own 

 clear insight so far overcame his faith in Alison that he found it 

 "not impossible that a certain degree of agitation might be occa- 

 sioned in the blood by the elastic resilience of the vessels reacting 

 on it, after the distending force of the heart has been withdrawn"; 

 and, in short, that the evidence in the case did not "warrant the 



* In a tract entitled Principia pro motu sanguinis per arterias determinando 

 Op. posth. XI, pp. 814-823, 1862. 



f "Sizes" is Owen's editorial emendation, which seems amply justified. 



