75 



substances into the digestive tract these products of hydrolytic 

 dissociation can as a rule be demonstrated very easily. This 

 suggests a rapid withdrawal from the blood by the tissues and 

 it seemed to me worthwhile to investigate this problem a little 

 more closely. 



We know that in nature the Echinoderms obtain their food 

 at very irregular intervals and I have often been impressed by 

 the fact that almost all marine animals are, so to say, in a state 

 of constant starvation. 



If this is true it must be of the utmost importance for the 

 animal to secure whatever it gets and whenever it get sit, in the 

 most rapid and effective way possible. Seen from this standpoint, 

 this rapid withdrawal of substances is without any doubt a 

 property which is highly purposeful in the struggle for life. 



There is one very essential feature by which these bloods 

 are entirely different from mammalian blood. They are in no 

 respect a store of anything, they are only a transmitting medium. 

 Nothing is stored in dissolved form ; the protein crystalloids, 

 described by List 81) and the fats contained in the interior 

 of the corpuscles, are not yet present in dissolved form, but 

 in formed elements. 



These bloods are not the carefully balanced system which 

 the blood of vertebrates represents ; they are just dissolving and 

 transporting media. The question whether they are absoluty 

 stagnant as has frequently been supposed, has been discussed 

 on p. 39. 



To study this question of the withdrawal of food constituents 

 from the perivisceral. fluid and to get some information about 

 the food-consumption by the tissues, I made the following set 

 of experiments on starfishes. Various quantities of either glucose 

 or glycine, being the most easily available monose and amino- 

 acid, were injected by means of a syringe into the coelomic 

 cavity. They had been dissolved in sea water and were distributed 

 as equally as possible over the whole system. To avoid the 

 objection that part of the injected fluid might have escaped 

 through the wound made by the injection, I first made the 

 following control experiments. Several starfishes into which a 

 large quantity of glucose had been injected, were put into a 

 finger-bowl in a minimal quantity of seawater. After an hour 

 or so this liquid was tested with Fehling and always gave 

 a completely negative result, even if Benedict's qualitative 

 reagent was used. The same tests in the case of glycocoll 

 gave a negative ninhydrin. 



Possibly this retention of injected fluids is due to a contraction 

 of the muscle tissue which is found everywhere under the peritoneal 

 epithelium, very much like when in intraveneous injection in 

 mammals no blood escapes. It may still have another explanation. 

 Cuenot 23) and 27), in his paper on the biological importance 



