THE COASTS OF SAINTONGE. 287 



the circulatory circle is incomplete, and when there 

 exists some sort of interval between the termination 

 of the arteries and the origin of the veins, the blood 

 itself falls into the general cavity of the body, and 

 its admixture is effected within that cavity. Such 

 is the case in Insects, Crustaceans, Molluscs, &c. 



When the circulatory circle is complete, when the 

 arteries and veins form a continuous circle, the repa- 

 ratory matters of the chyle and of the lymph can 

 only reach the blood by traversing the walls of the 

 blood-vessels. Certain of the Radiata and all the 

 Worms exhibit this phenomenon. 



But whatever may be the existing anatomical 

 dispositions, there is one fact which we observe 

 in all animals. In order to become adapted for 

 the nourishment of the animal and to be trans- 

 formed into blood, chyle, and lymph, all the materials 

 destined to repair the incessant losses depending on 

 the wear and tear of the organism must first be ex- 

 posed to the action of the air. Thus in the Verte- 

 brata the lymphatic vessels open into the veins, in 

 the immediate vicinity of the respiratory organs. 

 In the Invertebrata even, when the blood mixes 

 directly with the chyle and the lymph, the anatomical 

 dispositions bring about a precisely similar result. 



When the blood on the one hand and the chyle 

 and the lymph on the other, are enclosed in distinct 

 cavities without communicating with one another, it 

 becomes necessary that these two latter fluids should 

 each undergo a special respiratory action. Innume- 

 rable observations proved to me long ago that such 

 was the case. In the Worms more particularly, the 



