SYSTEMATIC ANALYSIS OF APPARATUS. 99 



each circuit a portion of the Blood passes through each 

 eliminating organ (after a sufficient number of circuits, 

 all the blood will be subjected to the action of each 

 organ), while the blood also receives, during some or all 

 of its circuits, its needed supplies. 



359. THE SIMPLE PLAN is MODIFIED in different ani- 

 mals and in man to meet the minor exigencies of the 

 case, but the general idea is the same wherever there is 

 a circulation. 



360. THE ORGA*N BY WHICH COOLING TAKES PLACE 

 CANNOT BE PAET OF A CLUSTER, as an extensive surface 

 exposed to the air is essential to rapid evaporation, and 

 this is found only in the skin. 



361. IT WILL BE EASILY UNDERSTOOD that the activ- 

 ities of different parts of the body must produce very 

 different quantities, as well as qualities, of substances to 

 be eliminated, and will require equally different quanti- 

 ties of supplies. 



362. IT WILL BE AS READILY INFERRED, that if more 

 substance is to be thrown off or received through one 

 organ than through another, there must be larger blood- 

 tubes, or more of them, leading to the organs having 

 most to do, and the number or size may be increased 

 until all the Blood of the circuit shall be included. 



363. CASES EXIST IN THE HUMAN BODY in which 

 the organs of supply or elimination require blood-tubes 

 of all sizes, from the diameter of a pin up to that of the 

 entire circuit. 



364. WHETHER THE BLOOD AT EVERY CIRCUIT MUST 

 BE SENT THROUGH AN ORGAN, WILL DEPEND UPON, 1st, 

 how fast the substance to be eliminated accumulates, 

 and how long it can remain with safety in the blood ; 

 and, 2d, how large a supply the Blood can receive at 

 each circuit, and how rapidly it is used. 



365. THE CIRCUMSTANCES HITHERTO MENTIONED do 



359. How is ? 860. Why ? 361. What ? 362. What ? 363. What ? 

 364. what ? 865. What said of ? 



