54 



THE PHYSIOLOGY OF EARTHWORMS 



From these analyses it is apparent that urea and ammonia occur 

 as metaboHc products in the tissues, notably the intestine, passing 

 from there into the blood or coelom and from thence to the 

 exterior via the nephridia. The ability of the intestinal wall to 

 form urea was first shown by Heidermanns (1937) who incubated 

 homogenates of this organ with "peptone" and obtained urea, this 

 substance not being formed when homogenates of the body wall 

 were incubated with the same substrate. The provision of arginine 

 or ornithine as substrate had no effect upon the elaboration of 

 urea and it was concluded that urea is not formed by the Krebs- 

 Henseleit series of reactions. 



Table 8 



Nitrogenous Content of Tissues of Two Earthworms 



(values mg%) 



P. posthuma 



gut 



NH3 



Urea 

 Creatinine 



4-3 



4-6 



44 



body 



L. terrestris 

 gut body 



3-6 

 2-1 



5-5 



Author 



Bahl. 1947b 



7-7 

 15-3 



3-3 

 1-6 



Heidermanns, 

 1937 



Heidermanns used simple water extracts in his work, and 

 repeating his observations Cohen and Lewis (1950) were also 

 unable to obtain a yield of urea when intestinal preparations of L. 

 terrestris were incubated with arginine. They were also unable to 

 find urea after incubation with "peptone", a result in direct 

 contrast to that of Heidermanns, and for which they were unable 

 to account. However, using tissue homogenates in phosphate 

 buffer solutions, arginase activity is found (Cohen and Lewis, 1950) 

 when the intestine alone is considered, but if the whole body is 

 macerated and incubated then no arginase is observed. The 

 optimal pH for the enzyme is pH 7-2-8-6, and a co-factor in the 

 form of 10-^M cobalt increases the activity. Fresh captured and 

 recently fed animals are found to possess only slight arginase 



