70 PHYSIOLOGY OF THE CIRCULATION. 



of this portion of the vital fluid is subservient to any 

 physiological uses. 



The first effect resulting from the peculiar form, 

 arrangement, and vital properties of the arteries, is a 

 diminished rate of discharge of blood from the 

 minute arterial ramifications into the capillaries and 

 veins. And this is a necessary consequence of the 

 established laws of hydraulics. For as any impedi- 

 ment to the passage of a fluid along its containing 

 tube is known to diminish the rate of discharge from 

 that tube, so, in like manner, must the impediments 

 to the passage of blood through the small arteries 

 cause the quantity of fluid leaving those vessels in a 

 given tune to be much less than what would escape 

 from them in the same time, supposing those obsta- 

 cles not to exist. 



The only objection which strikes me as likely to 

 be urged in opposition to this view is that embraced 

 in the old opinion, that the arterial blood flows from 

 the narrow to the wide portion of a conical tube, in 

 consequence of the aggregate area of the minute 

 arteries being greater than that of the aorta. But 

 even if this statement were correct though its truth 

 has certainly not been satisfactorily demonstrated 

 it is nevertheless quite clear, that the obstacle to the 

 blood's passage occasioned by the minute subdivision 

 of the main current of viscid fluid, will more than 

 counterbalance any advantage which might otherwise 

 have been derived from the jointly increased calibre 

 of the smaller arteries. So that the practical result, 

 viz. the rate of discharge of blood from those vessels, 

 will, as before stated, be precisely similar to what 



