AND ANIMAL LIFE. 409 



to occur at one part of life called its acme, it is 

 impossible or absurd to suppose that this same 

 acme shall at one time be present at 15, and at 

 another at 35 years. 



CCCCLXXXIX. After having weighed ma- 

 turely the reasoning of Dr CULLEN, and having 

 also reflected on the revolutions of the system, 

 on their concomitant circumstances or subsequent 

 effects I am persuaded that there are chan- 

 ges in the mode of circulation in every period 

 of life, which satisfactorily account for their 

 accompanying or succeeding phenomena, with- 

 out referring these changes to the organic de- 

 velopment or alterations of which he speaks. 



From youth to manhood the circulation has 

 evidently undergone great modification ; the re- 

 spirations are less frequent, and various organs 

 begin to assume a new or more important cha- 

 racter in the animal economy. The develop- 

 ment and support of these organs must neces- 

 sarily make a call upon the sanguiferous system, 

 and in proportion as the demands of the Internal 

 functions are increased, either by exercise or the 

 evolution of new powers, in the same ratio the 

 general or external distribution of the blood will 

 be diminished* 



CCCCLXC. The condition of the circula- 

 tion at this period I would call internal, not 

 wishing to imply, by this expression, a state ap- 



* Vide Chap. IV. 



