286 RAMBLES OF A NATURALIST. 



by digestion on the one hand, and by interstitial se- 

 cretion on the other. In Man and in all the Verte- 

 brata, the blood thus receives the chyle and the 

 lymph, and these two liquids, which proceed the one 

 from the digestive organs and the other from all 

 parts of the body, circulate in special vessels which 

 communicate by a common trunk with the system of 

 the blood-vessels. In consequence of this disposition 

 or mode of arrangement, the chyle and lymph remain 

 distinct from the blood and the other liquids which 

 bathe all our tissues. 



In the Invertebrata there are no lymphatics or 

 lacteals. Here, moreover, we miss that cellular or 

 connective tissue which lines all the interstices of the 

 different organs in the Vertebrata; and in conse- 

 quence of its absence we meet with large, empty, 

 free spaces or lacunae, which separate the organs. 

 The lymph and the chyle not being enclosed in 

 vessels fall into these spaces, which are thus filled 

 by the liquid which is being elaborated to repair the 

 losses of the blood. We may easily comprehend 

 from these few words how important a physiological 

 part must be played in the Invertebrata by the 

 general cavity which results from the presence of 

 these lacunae, and by the fluid enclosed within that 

 cavity. 



We have already observed that in the Vertebrata 

 the chyle and the lymph are poured directly into the 

 vascular apparatus of the blood by means of the 

 vessels which enclose them. In the Invertebrata, 

 where these vessels are wanting, this cannot occur ; 

 and here two cases may present themselves. When 



