2O4 VERA DANCHAKOFF. 



fact that the tissues of the organism do not exercise under normal 

 conditions any digestive power, and it is not definitely settled, 

 which of the various tissues, if any, besides those connected with 

 the digestive tract, are endowed with a digestive power. And 

 still there exist sufficient indications that the tissues of a multi- 

 cellular organism, besides those highly specialized of the digestive 

 tract, are equipped with enzymes which confer on them a diges- 

 tive power similar to that so characteristic of the special elements 

 in the digestive tract. If the tissues of a multicellular organism 

 be put under the stress of starvation, under which condition no 

 amino-acids will reach them from the absorbing surface of the 

 digestive tract, the tissues will in this case use up tissue proteins, 

 they themselves hydrolyze the proteins or digest them, which 

 work is made possible by the presence of enzymes in these cells. 

 And another example of digestive work performed by tissue cells 

 of a multicellular organism can be found in the growth of tissue 

 on artificial media. Here again the transplanted bits of tissue 

 do not find within the culture medium ready building stones for 

 the building up of their protoplasm in the form of amino-acids, 

 but only proteins of the blood plasma clot. Here again the cells 

 of the tissues themselves have a chance of performing the splitting 

 or digestion of the proteins, and they do it. In both these cases 

 we base our conclusions of the presence of enzymes in the tissue 

 cells on the results of the experiments: on the continuation of the 

 output of nitrogen by the organism during a diet free from 

 nitrogen in the starvation experiment, and on the further growth 

 of the tissue in the culture experiment. The fact only not the 

 mechanism of the digestive activity by tissue cells is determined 

 in both cases. 



Some information concerning the mechanism, or rather con- 

 cerning one of the mechanisms, by which cells of our body may 

 digest, i.e., split and assimilate protein may be gained by micro- 

 scopical study. And this study informs us that in embryos 

 developing from mesoblastic eggs, i.e., from eggs containing 

 great quantities of yolk, as for example, from birds eggs, all of 

 the tissues contain at an early stage a great quantity of yolk 

 granules in their cytoplasm, which are digested intracellularly 

 and assimilated. Endodermal cells as well as ectoderm and 

 mesoderm cells, even primitive germ cells, all are endowed with 



