78 THE VITAL FUNCTIONS. 



By watching attentively the motions of the glo- 

 bules, it will be perceived that they pass back- 

 wards and forwards through these passages, like 

 ebbing and flowing tides. 



All these phenomena may be observed with 

 greater distinctness when the food of the animal 

 contains colouring matter, capable of giving a 

 tinge to the nutritious fluid, and allowing of its 

 progress being traced into the granules which are 

 dispersed throughout the substance of the body. 

 Trembley is of opinion that these granules are 

 vesicular, and that they assume the colour they 

 are observed to have, from their becoming filled 

 with the coloured particles contained in the nou- 

 rishment. The granules which are nearest to 

 the cavity of the stomach are those which are 

 first tinged, and which therefore first imbibe the 

 nutritious juices : the others are coloured succes- 

 sively, in an order determined by their distance 

 from the surface of the stomach. Trembley 

 ascertained that a living hydra introduced into 

 the stomach of another hydra, was not in any 

 degree acted upon by the fluid secretions of that 

 organ, but came out uninjured. It often happens 

 that a hydra in its eagerness to transfer its victim 

 into its stomach, swallows several of its own ten- 

 tacula, which had encircled it ; but these tenta- 

 cula always ultimately come out of the stomach, 

 sometimes after having remained there twenty- 

 four hours, without the least detriment. 



