50 



the body by the blood-corpuscles. Sections of mussels kept in 

 such solutions for short periods, e.g. 18 hours, showed such 

 heavy loading of fat in the epithelium of gills, mantle and foot, 

 that it seemed very probable, that the cells of these epithelia 

 absorbed the fat directly from the solution. This could in fact 

 be demonstrated experimentally. Mussels with the valves wedged 

 open and suspended so that the mouth did not come down to 

 the surface of the liquid, showed the same absorption. 



Such results are surely remarkable, for no steatolytic enzyme 

 can be present here making the fats „fit" for resorption. They 

 indicate that at least some epithelia can absorb fat without 

 previous hydrolysis. Perhaps this is a general phenomenon, 

 perhaps there is some complicated colloid-chemical procedure 

 which forces fatty substances to be absorbed by every epithe- 

 lium. In that case our experiments would show nothing with 

 regard to the actual utilisation of fats by Echinoderms. 



The presence of fats in itself of course never proves the 

 presence of lipolytic enzymes. They may have been built up 

 just as well from carbohydrates, proteins, fatty acids and many 

 other substances as from fats. Biedermann found this true 

 for the liver of snails e.g. ; after a heavy meal of flour he always 

 found the liver cells full of fat droplets. 



There is still another thing which might favor this view, 

 namely the abnormally high respiratory quotient which Putter 

 observed in his Cucumaria grubei. He explains it by the as- 

 sumption of a butyric acid and methene fermentation '), in chapter 

 26 we shall will hear of another possible, indeed, a more probable 

 explanation, in the third place it may also be caused by trans- 

 formation of carbohydrate into fat. Cane-sugar f.i. can yield one 

 third of its weight in fat and at the same time ^/g of the total 

 quantity of its energy (Moore 87), etc.). If such processes take 

 place, much more COj is produced than corresponds with the 

 oxygen-intake. The R.Q. consequently is ) 1. 



17. LACTIC ACID DEVELOPMENT IN AUTOLYSATES 

 OF THE LIVER. 



In the preceding chapter we saw that an acid of some kind 

 was formed in our digests which made it hard to judge whether 

 fatty acids were actually produced or not. This spontaneous 

 development of acid seems to me to be of particular interest, 

 since 1 believe that we have to do here with a phenomenon 

 of a more general importance than one might expect. 



') Such fermentations are not very frequent and I am not impressed by the 

 validity of his arguments. To quote Frankel 138): „Sumpfgas (Methan, CH4) 

 entsteht nur bei Pflanzenfressern und Omnivoren im Darm, nicht aber in dem 

 der Fleischfresser . . . ." .,Es entsteht wohl nur aus Cellulose..." (p. 207). 



