ANIMAL MECHANICS. 



147 



which is only at the rate of iooo ft. per hour, or one-twentieth 

 part of the energy of the heart. 



When the railway was constructed from Trieste to Vienna, 

 a prize was offered for the locomotive Alp-engine, that could 

 lift its own weight through the greatest height in one hour. 

 The prize locomotive was the " Bavaria," which lifted herself 

 through 2700 ft. in one hour ; the greatest feat as yet accom- 

 plished on steep gradients. This result, remarkable as it is, is 

 only one-eighth part of the energy of the human heart. 



Professor Donders* gives an estimate of the force of the 

 heart, which exceeds considerably the result found by Profes- 

 sor Helmholtz, and by myself. He assumes the contents of the 

 left ventricle to be 0.188 kil., or 188 cubic centimeters, or 

 11.473 cu bic inches, a result intermediate between the capa- 

 cities of the hearts of the ox and horse, measured by Dr. Hales. 

 Measured in ounces, this capacity is 6.63 1 ounces, or more 

 than twice the capacity assumed by me. The blood pressure 

 is assumed by Donders at 3.21 meters, or 10.527 ft. ; and the 

 force of the right ventricle to be one-third of that of the left 

 ventricle. The other elements of his calculation are the same 

 as my own. From these data, the daily labouring force of the 

 heart comes out equal to 



87,400 kilogrammeters = 281.03 ft. toiis. 



This result, as might be anticipated from the assumed size of 

 the ventricle, is more than double that found by myself and 

 Helmholtz, from independent data. 



It may be useful to the reader to state here the results of 

 observers, subsequent to Dr. Hales, as to the pressure of the 

 blood in the large arteries of several animals. Dr. Hales ob- 

 served the maximum pressure in the arteries, as measured by 



* Physiologie, p. 109. 



L 2 



