HELMHOLTZ IN BERLIN 



Helmholtz showed that less heat might be given off 

 than could be estimated from the complete oxidation 

 of the food supplied, indicating that the oxidation 

 processes in the body were incomplete. He also 

 computed the amount of heat given off by various 

 channels as 2'6 per cent, in heating excrementitious 

 matters, 2'6 per cent, in warming the air of expira- 

 tion, 1 4' 7 per cent, by evaporation of the lungs, and 

 8o*i per cent, by evaporation of sweat and radiation 

 and conduction by the skin. These results have been 

 corroborated and extended by many subsequent ob- 

 servers, and it has been conclusively established that 

 the heat of the combustion of the food, as determined 

 by a calorimeter, is equal to the heat given off by an 

 animal ; in short, that an animal is a living calorimeter 

 in which the food stuffs are oxidised or burnt. 



A new investigation almost invariably demands the 

 use of new appliances. New ideas, new conceptions 

 of method, spring up in the mind of the experimenter, 

 and a call is at once made on his powers of invention. 

 This is felt even in a well-furnished laboratory, and of 

 course much more when the investigator enters on 

 what is a virgin field of research. Helmholtz, when 

 he began the investigation of muscular contraction, 

 had to invent many of his tools. About this period 

 his friend, Du Bois Reymond, was laying the founda- 

 tions of his life-long work on electro-physiology, and 

 he also invented many appliances. There is little 

 doubt Helmholtz and he assisted each other in de- 

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