36 



precipitate. This proves that Ca must certainly be present. 

 This is not strange since sea water also contains a fairly large 

 quantity of calcium. 



Carbonates are not present in large quantities, since if a small 

 quantity of the liquid is evaporated, the residue when treated 

 with hydrochloric acid, does not foam, 



Chlorides of course are present in large quantities, silver nitrate 

 gives a heavy precipitate. 



In the digestive fluids of Gastropods a large quantity of 

 proteins seems to be present. The same thing is true of the 

 larva of Tenebrio, even when the animals have been starving 

 for some time. It does not seem to be the case with the Echi- 

 noderms. On heating no precipitate is formed before evapo- 

 ration takes place. A xanthoproteic- and biuret-test gave ne- 

 gative results. Since the biuret-test is negative, no peptones 

 are present either. A ninhydrin is negative, no amino-acids 

 are present in that way, though the animals from which the 

 juice had been obtained, apparently were in full digestion. 



Di-sodium phosphate gives a precipitate in an ammoniacal 

 solution; this may indicate the presence of Mg, but since Ca 

 is present, it may be due to this metal. 



The precipitate with sodium carbonate, also indicates the 

 presence of Ca. Bichromate does not give a precipitate, Ba is 

 not present. 



The results of my own experiments and those of Bieder- 

 mann have been represented in table 5. 



Table 5. 



Composition of digestive fluids of different species from personal 

 observations and data of Biedermann. 



All constituents mentioned above do not explain the ob- 

 served acidity satisfactorily. The very small quantity of phos- 

 phates, if they are present at all, does not account for an 

 acidity which as Roaf 108) states may be as high of that of 

 a decimolar solution of di-hydrogen phosphate. 



In the chapter on excretion we will discuss the importance 

 of the excretion of uric acid into the lumen of the intestine. 

 In connection with the results reported on in that chapter it is 



