6*80 THEORY OF VITAL AFFINITY. 



and more blood generated in the lungs, of warm 

 than of cold blooded animals, that the compo- 

 sition of the former is renewed more rapidly, 

 their organization more highly developed, their 

 powers of resisting the ordinary forces of che- 

 mistry much greater ; and it is because the nu- 

 tritive process is more rapid in birds than in 

 mammalia, that the muscular power of the former 

 so greatly exceeds that of the latter. 



So long as any part of the body is supplied 

 with good arterial blood, and with a copious flow 

 of animal heat, by which its particles are united 

 with the solids, and kept in a state of perpetual 

 motion, chemical decomposition is prevented. But 

 whenever the process of nutrition is greatly dimi- 

 nished, as in scurvy, typhus, yellow fever, and 



causes it to contract with such force as to raise an immense 

 weight from the ground, until the water is expended, when the 

 weight descends. The reason of which is, that the particles of 

 the rope have a stronger attraction for those of water than for 

 each other without the intervention of a liquid. And such is the 

 vast force with which water combines with dry wood, that by in- 

 troducing dry wedges into the crevices of huge rocks, and keep- 

 ing them moist, they may be readily split open. Humboldt, 

 Cuvier, and some other physiologists, have maintained, that mus- 

 cular contractility is generated by the perpetual coagulation of 

 fibrin. And it must be confessed, that this explanation is a very 

 near approximation to the truth ; for it certainly does depend on 

 the union of fibrin with the muscular tissue, during which it be- 

 comes solid, as in the process of coagulation. But they seem not 

 to have had the slightest suspicion that caloric is the cause of 

 both coagulation and nutrition ; nor that the cohesive power of 

 all the organs is diminished by its expenditure. 



