336 CIRCULATION IN THE BLOOD-VESSELS. 



coats of the arteries, are also influences which favour the 

 blood's circulation. 



I cannot pass over this subject without noticing the fact, 

 that the vitality of tissues is essential to the circulation. 

 When life is impaired stagnation at once results, and the 

 blood in contact with the impaired structures coagulates. 

 This simple fact explains, as M. Lister has satisfactorily proved, 

 the stagnation and changes in the blood and vascular appar- 

 atus observed in inflammation. 



The flow of blood is, as we have already shown, constant 

 and rapid. It is kept up by a variable number of propelling 

 efforts of the heart in different animals. Thus this organ 

 beats, 



In the horse, . . from 32 to 38 times in a minute. 

 ass, . 45 to 48 ,. 



ox, . . . 40 to 50 

 sheep and goat, 70 to 80 

 ' pig, 70 to 80 



dog, . 90 to 100 



cat, . . 120 to 140 

 To Hering, professor in the veterinary school of Stuttgart, 

 is due the merit of ascertaining by experiment the rapidity 

 with which blood flows in all warm-blooded creatures. Ferro- 

 cyanide of potassium was injected by him into one jugular 

 vein of a horse, and blood received from the opposite vein 

 and tested. Hering determined that the round of the circu- 

 lation had been completed by the solution in from 25 to 30 

 seconds. Vierordt has repeated these experiments, and es- 

 timates the rapidity of the blood's flow, as follows : 

 In the horse the blood flows round the body in 28 -8 seconds. 

 dog 15-22 



goat 12-86 



rabbit 6-91 



