68 



other 138 mgr. The difference between these two figures is most 

 probably within the limits of error. If not, it is sufficiently 

 explained by the fact that proportionally more epithelial tissue 

 is present in the same quantity of radial sacs, since the muscular 

 wall of the stomach of course has also been included. 



These figures certainly do not favor of the assumption that 

 the radial sacs are the organs of enzyme secretion ; on the 

 contrary they prove that relatively just as much enzyme is 

 secreted by the stomach. In the chapter on the histology of the 

 two organs we have seen that the „granular" cells are present 

 in the stomach just as well as in the radial sacs; this affords 

 other evidence in the same direction '). 



There are, however, in the literature certain statements which 

 seem to make the other view more probable. One of these we 

 find in Cohnheim's paper. C o h n h e i m observed that if one 

 puts small pieces of mussel flesh or fibrin into the stomach of 

 an Asteropecten aurantiacus, „so wird es nicht verdaut da die 

 Fermente nicht in den Magen gelangen. Fiir die Thatigkeit des 

 Seesternmagens ist ein complicirter Bewegungsmechanismus notig 

 die das von dem iibrigen Tiere losgeloste Organ nicht mehr 

 leisten kann". He states that with some practice it is easy to 

 prepare the stomach free. I never succeeded in accomplishing 

 it without tearing the wall. I do not understand either how 

 one can bring a solid particle into these stomachs which con- 

 tract their sphincter as soon as the animal is treated roughly. 



For these reasons I have made similar experiments in a some- 

 what different way. The arms of a starfish were cut off at a 

 little distance from the disc. Ventrally each arm was now opened 

 carefully near the centre of the disc. The ducts of the radial 

 organs were located and prepared free from the dorsal mesen- 

 terium. This operation is exceedingly delicate and I had to 

 eliminate several animals before I succeeded in accomplishing 

 it. The ducts are very fragile and break at the least 

 touch. A ligature was now passed around the ducts after which 

 they were tied off firmly. The ducts were now cut distally and 

 the remainder of the arm was eliminated which is very easy 

 since they naturally break off at the articulation of the arm 

 with the disc (see p. 70). 



After all rays had been treated in this way, the stomach 

 was filled with a food substance in liquid form, be it a sugar 

 solution or a solution of some protein for which I usually took 

 casein — dialysed carefully — or K. L. I. M., a commercial milk 

 powder. The injection was made by means of a small hypodermic. 



These experiments had a double purpose. In the first place 

 I wanted to find out whether, asCohnheim found, the isolated 



') Chapeaux could extract enzymes even from oesophagus and rectum. 



