DIGESTIVE ACTIVITY OF MESENCHYME 433 



nite factors. This activity is, however, a part of the general 

 conditions governing the resistance to heteroplastic tissues, and, 

 as an easily demonstrable phenomenon, .may give some clues 

 to the understanding of other manifestations of the resistance of 

 organisms against heteroplastic grafting. 



2. MATERIAL AND ITS ARRANGEMENT 



The loose mesenchyme with its capacity for various differen- 

 tiation is a site of elaboration of a variety of products either 

 stored in its cellular derivatives or possibly given up' into the 

 organism. The introduction of various substances into the 

 organism stimulates the activity of the loose mesenchyme and 

 its cellular derivatives and may be followed even by a modifica- 

 tion of mesenchymal differentiation. The activity of the 

 mesenchyme and of its cellular derivatives as a possible factor 

 in the resistance of the organism against heteroplastic grafting 

 has been discussed in some of my previous papers.^- &. s. 7, s 



The formation of macrophages is of interest in connection with 

 the digestive power of the mesenchyme. Even during the 

 normal course of development groups of blood-corpuscles, for 

 example, may be cut off from the general circulation through 

 the rearrangement of embryonic vessels and numerous blood- 

 cells may be found free within the mesenchyme. Mesenchymal 

 cells are, then, isolated from the common syncytium and develop 

 a phagocytic activity against these stranded elements. This 

 fact alone demonstrates the digestive capacity inherent in the 

 mesenchymal cell in the developmental stage of a macrophage. 



Under ordinary conditions, cells do not often come into con- 

 tact with unmodified proteins. However, mesenchymal cells 

 may take up and digest any small unsplit particles of protein 

 of their own in the form of dead or weakened cells or cellular 

 debris with which they may be in contact. This they accom- 

 plish only with the aid of ferments capable of splitting proteins. 

 How far does this power of the mesenchymal cell extend? Does 

 it control heterogeneous proteins and heterogeneous living cells? 

 Is the digestive capacity of the mesenchymal cells an intracellular 

 property only or may they give off their ferments as a secretion 

 like the glandular cells of the endocrine organs? 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 29, NO. 4 



