60 



fehlt. Wasser und in ihm geloste feste Stoffe, die bei der Ver- 

 dauung entstehen, haben keine andere Moglichkeit zu den iibrigen 

 Organen, die sie ernahren sollen, zu gelangen als dass sie aus 

 dem Darm in die Leibeshohle eintreten und durch diese hindurch 



zu den andern Organen gelangen (p. 18)". 



/ 



E n r i q u e s has made a very extensive study of the anatomy and function 

 of this system, which consists of a dorsal mesenterial and a ventral anti-mesen- 

 terial complex of vessels. On the dorsal side we find a dorsal marginal 

 vessel over the whole length of the gut, adhering so firmly to its wall 

 that it can not be torn off. Between the ,,loop" of the intestine, it forms 

 a so-called transversal vessel. In the ,,oesophageal ring" there is a blood- 

 ring by which it communicates with the ventral vessel. From this ring 

 five vessels radiate out, following the five ambulacrae. There is also present a 

 ventral marginal vessel which splits further on into a left and right ventral mar- 

 ginal vessel. These communicate by means of the anterior and posterior trans- 

 verse vessels. From the right ventral marginal vessel the rete mirabile runs 

 over the whole gut and mesenteries. 



Other vessels go the water-lungs and to some other organs ; the genital 

 organs are also richly vasculated. 



Something of the same nature is also found in the sea-urchins and 

 starfishes. Here the whole system is much less complicated ; in the starfishes 

 it took a long time before it was discovered by Cuenot 25). 



E n r i q u e s first mentions that in studying the movements of 

 a body suspended in a liquid, one does not get a clear idea 

 of the real movements of such liquid (inertia). He succeeded by 

 means of a small syringe in bringing into one of the vessels 

 an oil drop which filled the whole vessel so that no water 

 could flow between the wall and the drop. He then registered the 

 movements of these drops photographically. He finds that the 

 oscillating movements of the blood, the pulsating of the vessels, 

 finally causes a gradual movement in one direction, moreover, 

 that the drop is broken down into two parts as soon as the 

 vessel branches into two. This process goes on and in this 

 way the fat is finally distributed all trough the blood system. This 

 is another proof for the effectiveness of the mixing in the blood 

 system. 



The vessels pulsate especially when they are full of liquid as 

 he could demonstrate by experiments in which he injected a 

 small quantity of sea water into a vessel. This is the case 

 during the period of resorption. 



A very interesting process of secretion (of enzymes?) is described by 

 Enriques. Greenish dichroitic granulae showing much similarity to the 

 liver secretion of Molluscs (Enriques) and whose enzymatic nature is 

 made probable by the fact that they stain brownish with osmic acid, are 

 formed in the cells of the wall of the vessels ; they are carried to the 

 gut-wall, sometimes by amibocytes, and penetrate into the lumen. Their 

 number increases during inanition. 



Let us now proceed to discuss Cohnheim's experiments 

 on absorption. A remarkable thing in all his experiments is that 

 he nearly always fills the intestine with 20 30 c.c. of liquid. Now, 



