What is the Use of Respiration.? 



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products and the heat, CO2, H2O, etc. liberated in respiration. 

 But we can not measure all the products and we can only inade- 

 quately apprehend what they are. Physiologists have come to 

 see that C0 2 is not the essential or invariable product of respira- 

 tion, but we have not yet realized that heat may not be the 

 essential, although it appears to be the invariable, product of 

 respiration in plants and in animals. The calorimetric experi- 

 ments above referred to show that only a small part of the heat 

 liberated can possibly be used by the living organism. May 

 we not, therefore, regard it as the end-product of a series of 

 reactions liberating or transforming energies? Some of the 

 energy may be converted into work; some may escape measure- 

 ment, whether converted into work or not, because we know 

 neither the energy nor the work; the unused (chemical?) energy 

 may escape, after transformation, as heat. 



Whether respiration is to be regarded as wasteful or not, 

 who can sav^ If the work to be done is essential, if the processes 

 are fundamental, and if, for their accomplishment, a certain 

 form or forms of energy are necessary, other forms being by- 

 products, then we can not regard respiration, any more than 

 wood-sawing, as wasteful. The heat liberated is, under certain 

 CDnditions, very useful; it may warm the chilly soil immediately 

 surrounding the sprouting seed; it may melt the snow about and 

 above the growing stalks of spring flowers and of those wild 

 plants which, the summer through, make their way through the 

 edges of snow banks high up on mountain sides. But, for the 

 most part, the heat liberated in respiration must be regarded as 

 useless, the end-product in a chain of unknown links. The 

 use of respiration would appear therefore, to consist not in the 

 liberation of energy escaping and measurable as heat, but in 

 supplying living organisms with necessary substances or with 

 energy in those needed forms which are accompanied by heat as 

 a by-product or end-product. 

 Stanford University, California. 



