150 . ANIMAL MECHANICS. 



The mean of all the pressures, including maxima and 

 minima, were found by Spengler (pp. 58, 9), to be, 



No. 



Horse. 



Dog. 



Goat. 





170 mm. 



185 mm. 



140 mm. 



2, 



175 » 







3, 



160 „ 



150 n 





4, 



165 „ 



165 „ 





Mean, 



167-5 mm. 



158-75 mm. 



140 mm. 



The rate at which the blood circulates through the body 

 may be estimated from the size of the left ventricle, as com- 

 pared with the total quantity of blood in the body. The total 

 quantity of blood in the body has been found by weighing, 

 before and after death, criminals executed by decapitation. 

 From such observations made by Lehmann, Weber, and 

 Bischoff, the total quantity was found to range from 9 lbs. to 

 10 lbs. If we assume the latter quantity, and take the capa- 

 city of the left ventricle at 3 ounces, it is plain that a quantity 

 of blood equal to that contained in all the vessels, will have 

 passed through the heart at the end of 53 strokes, which, if 

 the pulse be assumed at 75 to the minute, will correspond to 

 42 seconds. This represents the time occupied by the entire 

 circulation of the blood. The time occupied by absorption, 

 circulation, and secretion, combined, may be set down at less 

 than 4 minutes, as appears from the following interesting 

 experiment, devised by Professor Macnamara, of the Eoyal 

 College of Surgeons in Ireland, at which I had an opportunity 

 of assisting. An old soldier, a patient of the Meath Hospital, 

 suffering from rrydrocele, was trained by us to urinate at the 

 word of command, at intervals of one minute, into a succes- 

 sion of test tubes. When his training had been completed by 



