24 



is digested and melts away to a greyish mass which can scarcely 

 be discerned from the surrounding liver material. This problem 

 has also been studied by Stub el 125). These experiments seem 

 to show that the protein can only be dissolved by living liver- 

 cells and shows something of the nature of the activity of 

 the mesenterial filaments of the Actinians, as it was pictured 

 by Mesnil. Jordan 69) made moreover phagocytosis in 

 these animals probable. 



From this point of view an investigation of the Echinoderms 

 in this respect seemed most promising. It appeared however 

 that all the enzymes are found free here ; this group ranks 

 high as far as the physiology of its digestion is concerned. 



In order to get some definite information on this question, I 

 made a series of experiments on the digestive juice, as secured 

 from the intestine of fresh specimens. In Thyone and Arbacia 

 this is very easy, one simply punctures an isolated loop of 

 intestine, washed in sea water, which as a rule are full of 

 liquid. In Asterias the liquid was collected by pressing on the 

 outside of the stomach, after the arms had been cut off. The 

 few drops of liquids which appeared on the oral disc were then 

 collected. In this way I did not succeed of course in separating 

 the digestive juice completely from the perivisceral fluid. The 

 method however seems to be the only practicable one. 



To these liquids a certain quantity of substrate was added 

 in a deep-depression slide and a droplet of toluene. The whole 

 was covered with a cover-glass and as a rule evaporation was 

 prevented by the use of vaseline. The slides were then put 

 into the incubator at 37 C and inspected after different intervals 

 of time. 



It soon became evident that all the enzymes are present in 

 the free form. Our trypsin-like enzyme is present in a free 

 form in the digestive juices of every one of our three species. 

 Small shreds of fibrin were dissolved within 24 hours, the same 

 happened to pieces of gelatin. A positive ninhydrin which 

 test was negative in controls demonstrated the presence of 

 the products of enzymatic action. In some cases a positive 

 biuret for peptones could be obtained. 



No evidence whatsoever could be obtained of an amylolytic 

 action of the visceral fluid. A microscopical examination of 

 starch grains which had been digested with the digestive juices 

 for one, two or three days, did not reveal any changes. A 

 slight swelling takes place in the grains, probably due to the 

 alcalinity of the medium, but no trace of corrosion can be 

 observed. In one case I found a reduction of Fehling, but 

 a control showed that the starch used here was not entirely 

 trustworthy. 



These results are the same in starfish, urchin and cucumber 



