49 



vation has been made by Biedermann and Moritz on the 

 liver of HeHx 9) : „So erschienen etwas dickere Schnitte einer mit 

 Osmium behandelten Schneckenleber fast gleichmassig schwarz 

 und undurchsichtig" ; only in very thin sections could they see 

 the separate droplets. After about 10—20 hours this loading of the 

 epithelium with fat has reached its maximum, I obtained the best 

 results in specimens which had been injected in the late afternoon of 

 one day and dissected early in the morning of the next. The 

 staining of the fat by F 1 e m m i n g ' s fluid — one day — was very 

 incomplete in my sections, under high power the droplets were 

 perfectly clear and not black. The soap sections freed from 

 the soap, could easily be used for a test with Sudan III and I 

 have used this reagent in order to make sure that the droplets 

 which I had observed, actually were of fatty nature. Sections 

 thus treated gave a most splendid and enchanting sight, the 

 hundreds of droplets all colored reddish could be seen everywhere 

 and in every cell of the epithelium. In some of the sections of 

 later stages, the cell-border turned towards the intestinal lumen, 

 was fairly clear and free of globules. The fat then began to 

 accumulate in the sub-epithelial connective tissue in the same 

 way as many other substances — see the chapter on resorp- 

 tion in starfishes — . 



Some of the guts of Arbacia which had been treated in exactly 

 the same way, but which were imbedded in paraffin ■ — so that the 

 alcohols through which they passed, might have dissolved away the 

 fats — , gave very nice sections. The fat was stained very comple- 

 tely here and the sections immediately showed the presence of fat 

 by the many pitch-dark globules they contained. A piece of a 

 section of this kind has been drawn by Mr. H. van Laar, 

 who also made the other pictures for me'). (Fig. 4 of our plate). 



These results seem to indicate with a fair degree of certainty, 

 that fat is actually used and digested, but they do not give 

 us any evidence as to whether it is ingested as such after 

 having been emulsified (phagocytosis ?) or whether it is hydro- 

 lysed first. Our titration figures would prove that the latter 

 took place were it not for the formation of acid even in digests 

 without olive oil. Since however no emulsification takes place, 

 I am inclined to believe that hydrolysis actually occurs. 



There are some facts, however, which deserve a more general 

 attention in connection with the whole problem of the digestion of 

 fat. I mean the experiments of C h u r c h i 1 1 1 6) on the absorption 

 of fat by fresh-water mussels. 



Mussels were kept in soap solutions, prepared from olive oil, 

 both unstained and stained with Sudan III. Histological exami- 

 nation of such mussels and of controls revealed the fact that 

 fat is absorbed abundantly by all epithelia and carried all over 



I am very much obliged to him for this service. 



