144 



ANIMAL MECHANICS. 



statical force of the arterial blood in the ox, but there is rea- 

 son to believe that it is rather greater than in the horse, and 

 nearer to 10 ft. than 9 ft. If we are at liberty to assume it to 

 be 9.66 ft., which is the greatest height measured in the horse, 

 we can calculate the capillary coefficient as follows : — In the 

 ox, the capacity of the left ventricle was found by Dr. Hales 

 to be 12.5 cub. in., and the pulse beats 38 times in a minute- 

 Hence the capillary coefficient in the ox is — 



d> _ Q _ 12.5 x 38 _ 



A x l - h - 9.66 _ 39 ' 8 ; 



This coefficient is nearly the same as that of the horse, an 

 agreement which serves to show that the capillary resistance 

 depends more on the bulk of the animal than on any other 

 condition. 



If we suppose the coefficient of capillary resistance to be 

 the same in man as in the horse, we can calculate the hasma- 

 statical pressure of the blood in the human arteries, as fol- 

 lows : — The human heart has a capacity in its left ventricle, 

 when in action, of 3 ounces, or 5.2 cub. in. ; and beats 75 time3 

 in a minute. Solving equation (18) for h, we have 



Q 



h - 



A x T 



Substituting for Q the product of the capacity of the ven- 

 tricle and rate of pulse, and for the capillary resistance, its 

 value found for the horse we obtain 



h = $' 2 x 75 = . f eet 0 f bi 00( ]. 

 39-3 



This is the value that I shall assume for the arterial pressure 

 in man. This estimate of the blood pressure approaches to 

 that of Donders,* which is 10.527 ft. (3.21 metres). 



* Physiologie, p. 109. 



