246 COLLOIDS IN BIOLOGY AND MEDICINE 



readily diffusible peptones which have entered through the intestine 

 are again changed even in the intestinal wall into colloidal albumin; 

 sugar is retained in the liver as an animal starch or glycogen and so 

 on for other examples. 



This change into the colloidal condition is usually associated with 

 a metamorphosis into a substance native to the body from which 

 the cells and tissues of the organism are built up. It may be con- 

 cluded from the investigations of ALEXIS CARREL and BURROWS* 

 that the circulating nutritive fluid already contains all the elements 

 required for the most varied organs. These investigators suspended 

 pieces of tissue from freshly killed mammals in drops of plasma from 

 the same kind of animal. The tissues continued to grow, cartilage 

 produced cartilage, a spleen produced cells which resembled spleen 

 pulp, and pieces of kidney grew tubes of cells which resembled the 

 kidney tubules. 



The future will teach us whether we must regard this phenomenon 

 as a kind of crystallization. Perhaps it will be possible for future 

 colloid investigators to express the problem of cell nutrition in terms 

 of the brilliant side-chain theory of EHRLICH. To what extent the 

 fixation of colloid foodstuffs by the cell is a matter of chemical 

 forces or simple mechanical adsorption is an open question, which 

 so far must be decided differently in each individual case. 



Hitherto it has been only possible in the case of fats, to follow 

 visibly their course from the moment of resorption to their fixation 

 in body tissues. In the intestines 1 with the assistance of the 

 alkaline reaction of the intestinal fluids, the intestinal and pan- 

 creatic juices and the bile form a very fine emulsion of the fats. 

 Simultaneously, there occurs a splitting into fatty acids and glycerin 

 under the influence of ferments, Upases. It is not yet established 

 whether the splitting of the fats is complete, which would mean that 

 the intestine could only absorb dissolved fatty acid salts of alkalis 

 (soaps) and glycerin, or whether some of the fat remains unchanged 

 and is absorbed as such. If this latter statement is actually true, we 

 should have to assume that, under the influence of the surrounding 

 soap solution and possibly other factors, the surface tension of the 

 fat droplets is reduced to a minimum so that they may easily change 

 its shape or enlarge their surface and pass the very minute openings 

 in the intestinal epithelium. From page 16, we know that to produce 

 a change of form by pressure alone, there would be required forces 

 (many atmospheres) such as never occur in the organism. We have 

 in this case conditions similar to those in the case of leucocytes (see 



1 It is hardly possible to attribute great significance to saponification in the 

 stomach. 



