ANIMAL MECHANICS. 



143 



The average of the capacities of the left ventricles of the 

 hearts of six dogs examined by Dr. Hales is 0.954 cub. in. ; 

 and the average statical pressure in the arteries of sixteen 

 dogs experimented on by him is 4.75 ft. of blood ; and the 

 average pulse of the dog is found to be 97 beats in a minute. 

 Hence equation (18) will give us, for the coefficient depend- 

 ing on the capillary resistance in the dog, 



ft _ Q _ 0.954 x 97 



I h 4.71 



■=i 9 .6. 



These results, depending solely on the resistance offered by 

 the capillary vessels to the flow of blood, show by their 

 near approach to equality, that in animals, like the dog and 

 sheep, we may safely assume the resistance offered by the 

 structure of the capillaries to be nearly the same. 



The sheep and dog differ from each other considerably in 

 size of heart, rate of pulse, and haemastatical pressure of blood ; 

 yet, notwithstanding these differences, the capillary coefficient 

 depending on them all comes out to be nearly the same in 

 both animals. The capillary coefficient, found by experiments 

 made on the horse, comes out to be double that of the dog 

 and sheep, showing that the resistance to the circulation in 

 the horse is only half that of the smaller animals. 



The left ventricle of the horse contains 10 cub. in., and 

 the rate of pulse is 36 beats in a minute, while the average 

 haemastatical pressure of the blood in the arteries is 9.14 ft. of 

 blood ; hence, we obtain for the capillary coefficient in the 

 horse, 



. d* Q ioxq6 



ixT = T= = 39-3- 



l h 914 D J 



This quantity is double that found for the dog, and there- 

 fore the capillary resistance is one-half. 



Dr. Hales did not make any observations on the hsema- 



