122 Circulation of the Blood 



\varm, and vivified blood flowing in by the arteries in 

 its stead, which fresh blood cherishes and warms the 

 parts, and restores to them sense and motion ; nor 

 could the extremities be restored by the warmth of a 

 fire or other external heat, any more than those of 

 a dead body could be so recovered : they are only 

 brought to life again, as it were, by an influx of internal 

 warmth. And this indeed is the principal use and end 

 of the circulation ; it is that for which the blood is sent 

 on its ceaseless course, and to exert its influence con- 

 tinually in its circuit, to wit, that all parts dependent 

 on the primary innate heat may be retained alive, in 

 their state of vital and vegetative being, and apt to 

 perform their functions ; whilst, to use the language of 

 physiologists, they are sustained and actuated by the 

 inflowing heat and vital spirits. Thus, by the aid of 

 two extremes, viz. cold and heat, is the temperature of 

 the animal body retained at its mean. For as the air 

 inspired tempers the too great heat of the blood in the 

 lungs and centre of the body, and effects the expulsion 

 of suffocating fumes, so in its turn does the hot blood, 

 thrown by the arteries into all parts of the body, cherish 

 and nourish and keep them in life, defending them 

 from extinction through the power of external cold. 



It would, therefore, be in some sort unfair and extra- 

 ordinary did not every particle composing the body 

 enjoy the advantages of the circulation and transmuta- 

 tion of the blood ; the ends for which the circulation 

 was mainly established by nature would no longer be 

 effected. To conclude then : you see how circulation 

 may be accomplished without confusion or admixture 

 of humours, through the whole body, and each of its 

 individual parts, in the smaller as well as in the larger 

 vessels ; and all as matter of necessity and for the 

 general advantage ; without circulation, indeed, there 

 would be no restoration of chilled and exhausted parts, 

 no continuance of these in life ; since it is apparent 

 enough that the whole influence of the preservative 



