SYSTEMATIC ANALYSIS OP APPARATUS. 



FIG. 90. 



101 



Fig. 90, plan of compound cir- 

 culation ; 1, 2, two Hearts, enclosed 

 in one membrane, so that external- 

 ly they appear as a unit ; a, arteries 

 leading out of 1 and branching up- 

 ward and downward, and leading 

 into c, capillaries, through which 

 their contents can pass into v, veins 

 that open into 2, from which a" lead 

 into c", capillaries, through which 

 their contents can pass into v", 

 opening into 1. Thus a compound 

 circuit is formed, so that when the 

 Hearts alternately contract and re- 

 lax, they can pour their contents 

 through the entire course. The 

 whole of the Blood in this case 

 passes through the eliminating or- 

 gans, R, respiratory, also marked 

 lungs. 



A cluster of organs is represent- 

 ed by 4, 5, 6, 7, 8, 9, of which those 

 marked d are digestory, m, the 

 spleen, modificatory, and e, the kid- 

 neys, eliminatory. These receive 

 at each circulation a part of the 

 Blood thrown out by 1 downward, 

 and, after an uncertain number of 

 circulations, each of them must 

 have the opportunity of acting up- 

 on all the Blood, if it awaits their 

 action. It is also noticeable that 

 the Blood circulating through 4, 5, 

 6, 7, circulates through 8 before it 

 passes into the veins. 



1 is called the Left, Back, and 

 Systemic Heart its initials, S H; 

 a c and v are called Systemic Arte- 

 ries, Capillaries, and Veins, and 

 have the respective initials, S A, 

 S C, S V; 2 is called the Right 

 Front, Pulmonary, or Respiratory 

 Heart; a", c", v", are called the 

 Pulmonary or Respiratory Arteries, Capillaries, and Veins, having the 

 initials, PA, P C, P V, or R A, R C, R V. 



Describe Fig 90. How many arteries leading out from each Heart ? 

 many veins back ? 



How 



