CONTRACTILITY AND PHOSPHORESCENCE. 189 



The doubly refracting violin string corresponds to the doubly 

 refracting particles in muscle fibrils ; the water in the glass 

 represents the watery isotropic substance round the contractile 

 fibril, doing duty as refrigerant ; the spiral wire supplies the 

 place of the chemically active thermogenic molecules ; the clos- 

 ure of the galvanic circuit corresponds with the process of the 

 stimulation of the muscular element. 



Some physiologists object that the body of an organism or a 

 muscle "is sensibly uniform in temperature throughout, and 

 that the more work done, the more rapid the circulation ; and 

 the more certain this uniformity of temperature, the more it 

 seems to be impossible that such thermodynamic processes are 

 carried on in the animal system as are familiar to us in our 

 heat-engines." 1 



To the objection that the body of an organism, or muscle 

 cell, does not satisfy the conditions of a thermodynamic 

 machine because the temperature is uniform, Engelmann re- 

 plies that " we must assume, on the contrary, exceedingly large 

 differences of temperature in the stimulated muscle. What 

 holds good of the whole body holds good of the muscle also." 

 As Pfliiger observes, the temperature measured with our instru- 

 ments is but an arithmetical average, "comprising an infinite 

 number of different temperatures, pertaining to an infinite num- 

 ber of different points. 



" From the fact that at the contraction of the muscle an 

 infinitesimal part only of the muscular mass is chemically 

 active, we infer that the temperature of their particles must, at 

 the moment of combustion, be an uncommonly high one. Great 

 as the specific heat of muscular substance is, it would be im- 

 possible otherwise to account for a rise in temperature of the 

 whole mass even of 0.001 C., only. Without any exaggera- 

 tion, we must assume that the temperature of the chemically 

 active particles may, at the moment of combination, exceed the 

 average muscular temperature by hundreds of degrees. 



" Since each thermogenic particle is surrounded by a rela- 

 tively enormous cool mass, conducting heat and diathermous, 



1 Thurston, R. H. The Animal as a Machine and a Prime Motor, and the 

 Laws of Energetics. New York, 1894. 



