532 PHYSIOLOGY OF THE DOMESTIC ANIMALS. 



Various attempts have been made to calculate the time required by 

 the blood for making one complete circuit of the body. The method 

 ■which is generally accepted as giving reliable results is what is known 

 as the " transfusion method " of Hering, and consists in injecting into 

 one of the jugular veins toward the heart a solution of some salt, the 

 presence of which in the blood may be readily recognized by chemical 

 tests, and in finding how soon after the injection the salt appears in 

 the blood coming from the head in the corresponding vein on the 

 opposite side of the neck. As determined by Vierordt, the duration of 

 the circulation in different animals is as follows : — 



Horse, 



31.5 seconds. 



Goose, 



10.86 seconds. 



Dog, 



16.7 " 



Duck, 



10.64 " 



Rabbit, 



7.79 " 



Buzzard, 



6.73 " 



Hedgehog, 



7.61 " 



Fowl, 



5.17 " 



Cat, 



6.09 " 







By comparing these numbers with the frequency of the pulse in 

 these animals, the deduction has been made that the circulation is 

 accomplished in 27 heart-beats. From this the amount of blood thrown 

 out at each contraction of the ventricle may be calculated : for if the 

 entire amount of blood passes through the heart in 27 pulsations, one 

 pulsation will throw out ^ l T the total amount of blood in the body, and 

 placing this amount at, for example, j 1 ^ of the body weight in a man 

 weighing 65.8 kilos, the ventricles at each pulsation will discharge 187.5 

 grammes, the amount, of course, being the same for both ventricles. If 

 we assume that these data are approximately correct, the work done by 

 the heart may be calculated. One kilogramme-meter is a force which in 

 the unit of time can raise one kilo one meter high. If, therefore, the 

 left ventricle expels 0.188 gramme of blood against the pressure of blood 

 in the aorta (250 milligrammes of mercury or 3.21 meters of blood), the 

 work done at each systole is 0.188 X 3.21 = 0.604 kilogramme-meter. 

 If the number of beats is 75 per minute, then the work done in twenty- 

 four hours = (0.604 X 75 X 60 X 24) = 65,230. kilogramme-meters, 

 while the work done by the right ventricle, since the pressure in the 

 pulmonary artery is only one-third that of the aorta, will be one-third 

 this amount, or 21,740. kilogramme-meters: and both ventricles together 

 will do a work of 86,907. kilogramme-meters in the twenty-four hours. 

 Since part of this work is converted into heat, the contractions of the 

 heart assist in maintaining the bodj r temperature. 



In the case of the ox it has been estimated that 0.75 liter of blood 

 is driven from the left ventricle at each systole, and since the pulse 

 in this animal averages 50 per minute 37.50 liters of blood will pass 

 through the heart in each minute, or 900 liters in twenty-four hours. 

 The specific gravity of the blood being 1045, 18,810 pounds of blood, or 



