15 



secreted by the skin (p. 381 ; uric acid?). Schiemenz 11 5) does 

 not believe in any toxic action. 



A sea-watery extract was made of a large number of starfish- 

 stomachs. Since the substance to be studied might be destroyed 

 by heat, the extract was made in the cold by vigorous shaking. 

 In order to avoid decay the extraction was not continued longer 

 than about four hours. The mass was now filtered and the 

 filtrate used for the following experiments. 



In the first place the action of this extract on the heart of 

 the bivalve Pecten was studied. This proved to be a very 

 typical one. 



The heart of Pecten can be isolated very easily. If one 

 pulls the two shells which the animal always keeps open in 

 its natural environment, apart, one easily succeeds in tearing 

 the adductor muscle into two. If this is done carefully, the 

 heart is found in absolutely uninjured condition right under the 

 muscle. It is found beating in its pericard which contains a 

 fairly large quantity of „coelomic" liquid. If left alone the 

 heart will continue to beat for a considerable length of time, 

 as control experiments showed. 



By means of a small injection-syringe the stomach extract 

 was now dripped on the beating heart in a fine stream. The 

 first beats are perfectly normal and do not show any effect of 

 the fluid on the beating. But by and by the beats come at shorter 

 intervals and finally a highly accelerated and irregular beating 

 results. Though no counts were made, I dare say that the heart beats 

 more than three times as fast as usually. If the irrigation is conti- 

 nued, the reverse happens after some time. Gradually the rate 

 of heart-beats slows down, till it falls below the normal rate 

 and finally the heart stops in a contracted condition. The 

 whole process takes place in only a few minutes and strongly 

 impresses one that it is due to a toxic action of some kind of 

 the extract. The poison would in that way have a stimulating 

 effect at first and finally cause the stopping of the heart in 

 contracted condition. 



Experiments of the same kind were made on the adductor 

 muscle of Pecten. Here however I did not succeed in obtaining 

 satisfactory results, though I was impressed of the fact that 

 the muscle weakened down after an initially vigorous reaction 

 to the fluid. Several trials for a graphical registration of this 

 fact gave disappointing results. By means of a light pulley the 

 movements of one free shell — the other shell was clamped 

 in a stand, while the open side of the shell was pointed 

 upwards — were transmitted to a counterbalanced lever, 

 writing on a drum, but the quite irregular behavior of the 

 muscle made these experiments a failure. 



Better results were however obtained with a frog's gastrocne- 

 mius. At regular intervals of 30 seconds the muscle was stimulated 



