!<)(> .\\\i i u>\. 



ol' \icarious action occurs bet\\eeu the capillary vessels of the skin 

 :md those of the respiratory sacs, So that \\hen the circulation pro- 

 cceds languidly tlin>ii"Ji om- sd of \essels, it is carried on with 

 :ler aeliyitx in the other. 



Fig. 80. 

 1 2 3 



(288.) The vessels appropriated to the distribution of the circu- 

 lating ilnid in the leech are rudely sketched iu.//ir. 80, 8. Then- is 

 no heart, Imt the movements of the blood arc entirely dne to the 

 contractions of the canals in which il Hows. The principal vascu- 

 lar trunks are four in number, which, although they all communi- 

 cate extensively with each other, perform distinct ollices in cllcct- 

 ing the circulation; two of them being specially connected \sith 

 the supply of the general system, while the other two seem sub 

 scnicnt to the distribution of the blood over the respiratory 

 saecnli. 



