THE PHYSIOLOGY OF EXCRETION. 8 1 



During the metabolism of the cell waste products (oxidized 

 plasm) are formed, which are expelled from the cell in the form 

 of small granules, concerning the fate of which I have now to 

 speak. 



These granules are either discharged into the body cavity 

 or into the vascular spaces, or they remain on the surface of 

 the cell between the connective tissue elements. Their fur- 

 ther fate is dependent upon certain cells, the function of which 

 I discovered in these animals, and which I call excretophores. 

 These excretophores are large cells, originating in the endo- 

 thelium of the body cavity. Certain endothelial cells liberate 

 themselves from the walls of the coelomic cavities, and assume 

 a wandering mode of life. In this state they are comparatively 

 small cells with a distinct oval nucleus and no apparent outer 

 membrane. The protoplasm appears in the living cell to be 

 very finely granular, and the living cell is in a state of continual 

 motion. The cell sends forth pseudopodia, by the aid of which 

 it moves about in the body, and during this wandering accumu- 

 lates the excretory granules which I have mentioned before. 



Part of the excretophores lie in the coelomic cavity; others 

 wander between the tissues, and wherever a foreign particle 

 comes in their way it is picked up and imbedded in the cyto- 

 plasm. This picking up of foreign matters is merely a mechani- 

 cal process which is well known in Amoeba, in the Myxomy- 

 cetes, and in the leucocytes of the higher Vertebrates. In the 

 latter this process plays an important part in pathology under 

 the name of phagocytosis. 



If an Amoeba creeps upon some substratum, it sends forth 

 pseudopodia in one direction, and the main body containing 

 the nucleus follows by the law of cohesion. This motion is not 

 merely an advance in one direction, but it is a complicated vor- 

 tical motion, as Ryder has shown. We can compare it to a 

 natural stream, where the motion in the middle is quickest, 

 whereas the two sides move slower, this being still more com- 

 plicated by the fact that the water at the surface moves more 

 rapidly than that at the bottom. In an Amoeba this is even 

 more pronounced than in a stream of water. By this vortical 

 motion all the small particles which adhere to the surface are 



