DIGESTIVE ACTIVITY OF MESENCHYME 461 



and adult spleen might have undergone an injurious effect 

 dependent upon the manipulation of mixing them with another 

 tissue, and, therefore, might in this experiment have become more 

 accessible to the phagocytic action of the splenic mesenchymal 

 cells. A series of experiments seemed necessary in which mixed 

 grafts of tumor and embryonic spleen should be made, in order 

 to obtain direct data concerning the phagocytic and digestive 

 capacity of the embryonic splenic mesenchyme in respect to the 

 growing Ehrlich sarcoma cells. 



A preliminary study of single embryonic spleen grafts has 

 shown that its mesenchyme undergoes within the allantois a 

 rapid granuloblastic transformation. While in general similar 

 to the growth processes observed in adult splenic grafts, the 

 changes which take place in the embryonic mesenchyme are 

 more rapid and more extensive. They also differ in certain details. 

 The embryonic tissue of the spleen, comparable to a cavernous 

 tissue, being, in fact, represented practically by the red pulp 

 part of the spleen alone, is always seen in the graft to be supplied 

 bj^ a rich vascular net. The vascular net of the embrj^onic 

 spleen after grafting rapidly joins with the allantoic vessels, and 

 thus the graft of embryonic splenic tissue ordinarily survives 

 in toto. It appears in sections as strands and islands of mesen- 

 chyme traversed and surrounded by large meshes of thin-walled 

 vascular channels. This mesenchyrne is seen to proliferate and 

 to undergo a rapid myeloid transformation; granuloblasts and 

 granular leucocytes — products of this metaplasia — find easy 

 access into the lumina of the thin-walled meshes of the vascular 

 net and are at least partly carried away. The granulocytes do 

 not, therefore, accumulate in excessive numbers and do not 

 form large agglomerations as in the adult splenic graft, in which 

 these often undergo a consecutive necrosis. Grafts of embry- 

 onic splenic tissue do not in general contain necrotic foci and, 

 what is of interest, do not call forth a myeloid metaplasia in the 

 host 's mesenchyme. 



In order to study the functional potencies of the embryonic 

 splenic mesenchyme in relation to the phagocytic and digestive 

 capacity, embryonic spleens of the seventh, the fifteenth, and the 



