EFFECTS OF MUSCULAR EXERCISE. 123 



compressing the interjacent blood-vessels, and forc- 

 ing onwards the current of the contained blood by 

 their successive contractions. Muscular action is, 

 indeed, one of the powers provided for effecting a 

 regular circulation. And hence when its assistance 

 is neglected, as it is by those who take no active 

 exercise, the blood begins to flow less freely, till at 

 last it finds some difficulty in returning against the 

 law of gravitation from the depending parts, which 

 \hen gradually swell. People engaged for years 

 in sedentary professions are thus very subject to 

 varicose or dilated veins and swelled feet. 



The chain of connexion among all the living func- 

 tions is nowhere more visible than in this relation 

 between muscular exercise and the circulation of 

 the blood. Action requires the presence of arterial 

 blood ; and in the case of the muscles, the very cir- 

 cumstance of their being active favours the circula- 

 tion and increases the supply. This increase, in its 

 turn, enables the parts to which it is sent to act with 

 greater energy and effect, and the augmented action 

 is attended by corresponding waste and exhalation. 

 To replenish the blood thus exhausted of its nutri- 

 tive principle, a greater quantity of food is required ; 

 and, to prompt us to attend to this condition, the 

 appetite becomes keener and more imperative, and 

 the powers of digestion proportionally vigorous. 

 The food taken is more speedily converted into 

 chyle, its absorption from the surface of the intes- 

 tines and transmission into the circulating current 

 more rapid ; and that the blood thus improved may 

 be properly and quickly animalized in the laboratory 

 of the lungs, respiration becomes deeper and more 

 frequent, thus admitting a larger quantity of air and 

 freer circulation through them than before ; and the 

 blood, thus renewed and re-endowed with the pabu- 

 lum of life, imparts fresh nutriment and vigour to 

 all the organs of the body, and fits them for that 

 active exertion which the proper discharge of his 



