392 THE LAWS OF OllGANIC 



example, when they have been chased or driven 

 for a great distance, it has been repeatedly prov- 

 ed that the blood will not coagulate, conse- 

 quently, that it is deprived of its ordinary vitality. 

 This phenomenon will be found to arise from 

 certain physical conditions of the blood, some- 

 what similar to those peculiar to depressing pas- 

 sions. Moderate exercise augments vitality, be- 

 cause the sanguineous fluid is favourably cir- 

 cumstanced for its more perfect oxygenation ; 

 indeed, it very often exhibits the buffy crust, as 

 in cases of inflammation ; but when this exer- 

 cise is accompanied by great debility, we have 

 other effects. 



CCCCLXVI. Excessive exercise is attended 

 by a great expenditure of the properties of the 

 blood, and of those materials that the system has re- 

 ceived for nutrition. Great exercise, before it 

 gives rise to debility, is maintained at the ex- 

 pence of the nutritive qualities of the sys- 

 tem, which, under the present circumstances, 

 are more quickly dissipated than on ordinary 

 occasions. The blood is more than usually 

 stimulating ; and, moreover, its circulation is 

 augmented in every respect. The existence 

 of these causes in some measure proves, that, if 

 great exercise be long continued, the blood will 

 speedily be impoverished. If we even suppose 

 the lungs to receive the natural, or even a greater 

 quantity of oxygen, this cannot supply the want 



