86 ON THE USE AND OFFICES 



" must they have returning vessels ? Is there 

 •' not a great difference between an animal \vhich, 

 " after the first few years, has no increase, and 

 " a being that increases from every joint, and is 

 *' supposed, therefore, to draw up only those juices 

 *' necessary for that increase j especially as the sap 

 *' is the liquid of the earth, not the blood of the 

 " tree, as is easily proved by adding nurture to 

 " the ground, when the sap fails, which soon 

 " restores it ? Besides, how is the circulation 

 " to be effected in the eternally increasing 

 " branches of a tree, whose every additional 

 " twig must make a variation in the quantity of 

 "juices wanted? Whereas, it is naturally de- 

 " creased as it mounts, by throwing out new 

 " shoots and branches, which expend the liquor 

 *' as it rises. And I believe I may say, that I 

 *' am now so well acquainted with all the differ- 

 " ent vessels of a tree, that I can no longer fail 

 " from ignorance : but here, except the inner 

 *' bark vessels all proceed in a different direc- 

 " tion, either round the tree, or from the centre 

 " to the circumference, how is it possible that 

 *' such large and powerful parts should be in- 

 ** visible ^ 



••' The use of dissection is to correct the use 

 " of imagination, or those experiments which 

 " have that effect, forcing the juices into chan- 

 ge 



