ANIMAL MECHANICS. 



141 



tion of projection of the maximum range on the plane AB, 

 bisects the angle CAB, and that 



72 cos 2 z z ,v 



h = - ; (16) 



4 cos 2 e 



where 



h = the unknown height due to the velocity of projection ; 



R = the maximum range AB = 8.773 ft. 



i - the angle made by AB with the horizon = 24° 14' ; 



e = the angle of elevation, made by AX with the horizon = 32 0 53'. 



Substituting the preceding values in equation (16), I find 



h = 2.586 ft.; 



and since the velocity of projection, v, is given by the equa- 

 tion, 



v=v / 2gh; (17) 



it follows that 



v = 12.905 ft. 



The result here found shows that the heart of man, when 

 experiencing the minimum of resistance, such as that offered 

 by the circulation when a large artery is divided, or the vessels 

 nearly empty of blood, contracts with a force measured by 

 2.58 ft. of a vertical column of blood. The heart of the horse, 

 under similar circumstances, contracts with a force measured 

 by a column 2.53 ft. in height. 



The following considerations lead us to the conclusion that 

 it is probable that the maximum hydrostatical force of man's 

 heart is nearly the same as that of the horse. The experiments 

 of Dr. Hales, fully corroborated by the recent observations ot 

 Poiseuille, show that the hydrostatical pressure of the blood is 

 the same in all the arteries of the same animal, that have a 

 sensible diameter ; from which fact, it is plain that the resist- 

 ance to the circulation of the blood takes place in the capil- 

 lary arteries and veins. If therefore we knew the relative 



