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8. AUTOLYSIS IN ECHINODERM GUTS. 



Discussing the presence or absence of proteolytic enzymes 

 in Holothuria tubulosa Cohnheim 17) states that he could not 

 observe a trace of autolysis in their guts, if they were kept 

 under aseptic conditions. This observation is doubtlessly right ; 

 I could observe something similar in our Thyone, its gut can 

 be kept for an almost indefinite length of time in sea water 

 under toluene without showing signs of profound changes. 

 Is this however an argument in favor of his contention that 

 Holothurians should have no proteolytic enzyme in their gut 

 and that the N-metabolism of this group does not atrount to 

 anything ? 



I do not believe it. In the first place we must remember 

 that the gut of these animals is strongly muscular and that 

 muscle-tissue autolyses much less completely and rapidly than 

 any other kind of tissue. It is very well possible that the 

 epithelium of these guts autolyses away while the muscular 

 wall keeps its coherency and gives the impression of being the 

 whole gut. As a matter of fact we can observe a change in 

 color and other changes in these guts allthough they do not 

 fall to pieces. 



To settle this argument and to find out whether Cohnheim 

 is right in his conclusions, I decided to study autolysis of the 

 guts of Asterias and- Thyone a little more in detail. In Asterias 

 nobody will doubt the presence of a proteolytic enzyme and 

 yet autolysis proves to be exceedingly slow even in this case. 



For this research I ground up a large quantity of radial 

 sacs and of stomachs of Asterias with sand. Some water was 

 added to these masses, a large quantity of toluene and a trace 

 of Na 2 CO 3 in order to keep the reaction of the digests in the 

 neighbourhood of neutrality. 



The digests were then put into the 37 C incubator and left 

 there to autolyse. At different intervals I made tests for pep- 

 tones and amino-acids by means of the biuret reaction and 

 ninhydrin on the protein-free filtrate. The proteins were as a 

 rule precipitated with 5 / trichloracetic acid. The liquid as 

 it came through the filter was clear, but not completely color- 

 less, perhaps on account of the fact that a small quantity of 

 a water soluble pigment which proved to be very troublesome 

 in all these experiments, was not precipitated out. 



After six days all these tests gave completely negative results. 

 After nine days I got a positive peptone-biuret in the radial 

 sac sample, but no evidence whatsoever was seen of autolysis 

 in the stomach sample. 



The radial sac sample became one homogeneous mass, but 

 the stomachs did not seem to be liquified, they could still 

 be seen separately. 



