348 SCIENCE PROGRESS. 



If it be decided that the fat is taken up by the columnar 

 cells, we ask, in what form is it absorbed, and by what 

 means do the cells accomplish their end ? 



There are two main theories : the one, that the fat is 

 absorbed in corpuscular form as minute globules of an 

 emulsion ; the other, that it is in some way first got into 

 solution, and the solution absorbed, the fat being subse- 

 quently again separated from the solution. 



It has been advanced against the corpuscular theory, 

 which appears to be the more prevalent of the two, that the 

 epithelial cells refuse to take up minute particles offered to 

 them. 



Donders could get no evidence of " choroidal " pigment 

 grains in the cells after feeding the animals on eyes, and 

 Griinhagen could not succeed in making the cells lining the 

 frog's gut take up particles of carmine. Tomasini has, how- 

 ever, lately maintained that starch granules, as such, can be 

 taken up and recognised in situ by iodine. Then, again, in 

 the microscopic preparations the fat particles are not seen 

 in the basal band, or even immediately beneath it as a rule, 

 but first appear at some distance within the protoplasm of 

 the cell. The emulsion, too, of fat within the digesting 

 gut is said by Cash to be not fine enough for the purpose, 

 and Krehl, who fixed the whole gut with its contents in the 

 case of Triton fed with cream, while he saw fine fat grains 

 in the cells, only found conglomerate masses in the lumen 

 of the gut. Certainly the fat does not attain the fine state 

 of division which we know as the " molecular basis " of the 

 chyle until it has actually passed the wall of the central 

 lacteal, and unless we imagine a special " selective power " 

 for the cylinder cells, it is difficult to explain why they 

 should refuse a carmine particle but take a fat grain. Even 

 the exsected gut of the frog, as Griinhagen has shown, will 

 take up olive oil, especially when it is also supplied with the 

 animal's bile, but refuses carmine particles. 



The theory of the absorption of fat in solution was 

 originated by Perewoznikoff, and shortly after developed by 

 Will. The idea is that from the fatty acids set free by the 

 action of the pancreatic ferment, soaps are formed with the 



