74 OYSTERS, AND ALL ABOUT THEM. 



Instead of what is, properly speaking, a brain, two 

 minute detached nodules are observable, each having a few 

 slender threads passing to the neighbouring parts, the 

 longest being affixed to the gullet, and thus it is evident 

 that the chief preserving sense is given to test the articles 

 of food. 



The heart, a beautiful structure, is situated in a cavity 

 between the folds of the intestine. It has two chambers : 

 an auricle, and a ventricle, from the stomach. The auricle 

 has walls, extremely thin, composed of the most delicate 

 bundles of muscular fibre ; it receives the blood from the 

 respiratory apparatus, and, by contracting, transmits it 

 through two intermediate canals into the more muscular 

 ventricle, from whence it is propelled throughout the body. 

 The vessels connected with it are as admirably adapted to 

 iheir proper service, and are as beautifully arranged as 

 these parts are in the camel, the elephant, or even in man. 

 There are three principal branches : one leading to the 

 mouth, the second leading to the liver and stomach, and 

 the third to the hinder part of the body. 



The fluid contained in the heart does not coagulate 

 spontaneously, and it holds in solution the same proportion 

 of sea-salt with the surrounding water. Two other re- 

 markable facts may be noticed ; the muscular flesh of the 

 ventricle is soft and tender, like that of a chick in the first 

 stage of incubation ; the auricle is of a black colour 

 throughout its tissue. 



Another power is still required : 



'* The vital air 



Pervades the swarming seas and heaving earths, 

 Where teeming Nature broods her myriad births ; 

 Fills the fine lungs of all that breathe or bud, 



