SYSTEMATIC ANALYSIS OF APPARATUS. 93 



333. Excretion is the name given to that part of 

 the process by which the useless substance is removed. 



334. Nutrition is the name given to that part of the 

 process by which the organs are renewed. 



335. THERE is ANOTHER CONDITION ESSENTIAL TO 



THE HEALTHY ACTION OF THE MENTORY ORGANS I they 



must be kept at certain temperatures, for which 



336. THEY MUST BE warmed, on the one hand, if 

 too cool, and cooled, on the other, if too warm ; hence, 



337. THE HEALTHY ACTION OF THE MENTORY OR- 

 GANS REQUIRES that provision be made for accomplishing 

 four objects or processes : Excretion, Nutrition, Warm- 

 ing, and Cooling. 



338. ALL FOUR OBJECTS CAN BE ACCOMPLISHED by 

 a very simple arrangement. 



339. Let minute tubes, smaller than hairs, and with 

 sides thinner than those of a soap-bubble, be interwoven 

 like a network through all the active parts of the organs, 

 and connected with two sets of tubes, one opening into, 

 and the other out from, the network; let these two sets 

 of tubes be also connected with a pump that shall receive 

 the contents of one and pour them out into the other ; 

 then fill this piece of mechanism with a proper fluid, and 

 connect with it certain arrangements to maintain the 

 supply in a perfect condition, and the circuit is com- 

 plete for supplying each of the four necessities of the 

 organs. 



One set of tubes. 



Network. Pump. 



Second set of tubes. 



340. THE CAPILLARY (hair-like) TUBES OR VESSELS 

 is the name of a set of microscopic tubes, that, in the 

 form of a network, are interwoven through the active 

 parts of all organs. 



833. What ? 834. What ? 835. What ? 386. How ? 337. What does 1 

 888. How? 389. Describe a proper mechanism. Write table. 840. What? 



