Prof. TyndalFs Notes on Scientific History, 41 



into harmony with the great law of conservation, which he 

 himself, alone and unaided, had thought out. 



44. Here follow a few of Mayer's remarks on muscular motion. 



In the first part of this memoir, the part played by combus- 

 tion in inorganic apparatus in the steam-engine, for instance 

 was, in its main characters, explained. Our present problem is 

 to consider the phenomena of vitality in connexion with their 

 physical causes, and thus give to the propositions of physiology 

 the basis of exact science. 



45. It has been already stated that an active working man 

 converts in a day 0*19 lb. of carbon into mechanical effect. 

 The weight of the whole muscles of such a man, who weighs 

 150 lbs., is 64 lbs. ; and, subtracting 77 per cent/of water, 15 lbs. 

 of dry combustible material remains. Let it be assumed (though 

 not granted) that the heat-giving power of this mass (with 

 40 per cent, of nitrogen and oxygen) is equal to that of an 

 equal mass of pure carbon ; then, if the work were done at the 

 expense of the muscles themselves, the whole of the muscles 

 must be oxidized and consumed in mechanical effect in eighty 

 days. 



46. This arithmetical deduction becomes still more evident 

 if we confine our attention to the work performed by a single 

 muscle — the heart. I assume, with Valentin, the quantity of 

 blood in the left ventricle to be at every systole on an average 

 150 cubic centimetres. The hydrostatic pressure of the blood 

 in the arteries is, according to Poiseuille, equal to the pressure 

 of a column of mercury 16 centimetres in height. The me- 

 chanical work done by the left ventricle during a systole may be 

 calculated from these data. It is equal to the raising of a 

 column of mercury ]6 centimetres long, and with a base of a 

 square centimetre to a height of 150 centimetres. The weight 

 of the mercury amounts to 217 grammes. The mechanical effect 

 of a systole therefore is 



{325*6 grammes raised 1 metre, 

 2 lbs. „ 1 foot, 



which is equivalent to 0'887 of a thermal unit, or equivalent to 

 the combustion of 0-0001037 of a gramme of carbon. Taking 

 for a minute 70 strokes, and for a day 100800 strokes of the 

 pulse, the work done by the left ventricle in a day is equivalent 

 to the raising of 202000 lbs. to a height of one foot. This is 

 equal to 89428 thermal units, which is equal to the combustion 



of -J -iflo.o ' fof carbon. According to Valentin, the 



work done by the right ventricle is half that done by the left. 

 The work of both chambers in a single day is therefore equal to 



