LETTERS TO BROTHER JOHN. 121 



LETTER V. 



224 Slackfriars Road, 



15th May, 1836. 

 MY DEAR JOHN, 



T HAVE now to speak of the principal actions con- 

 cerned in the nutrition of our bodies that is, in 

 converting our food into ourselves. These are four 

 in number : ABSORPTION, CIRCULATION, RESPIRA- 

 TION, and SECRETION. 



If you have read attentively what I have already 

 written concerning the absorbent vessels, and con- 

 cerning those arteries which, when convoluted and 

 conglomerated into those little balls called glands, 

 perform the office of secreting the several juices of 

 the body, as the saliva, &c. ; if, I say, you have 

 read all this with attention, you will now have no 

 difficulty in understanding what is meant by the 

 terms ABSORPTION and SECRETION. I shall now, 

 therefore, briefly describe the circulation of the 

 blood, and the effect which respiration has upon it : 

 and then I shall endeavour to exhibit to you these 

 important phaenomena of ABSORPTION, CIRCULATION, 



