THE HISTOGENESIS OF DENSE LYMPHATIC TISSUE 189 



tensive the inflammation, the greater seems the production of 

 eosinophiles. 



The close association of blood vessels of the connective tissue 

 with the groups of eosinophiles has already been mentioned. 

 This is partially explained when it is recalled that some of these 

 eosinophiles in the connective tissue are of the type found in the 

 blood stream, which have wandered out through the capillary 

 endothelium into the surrounding tissue. But there is an equally 

 close association between the blood vessels and the granulo- 

 poietic foci of connective-tissue eosinophiles. Groups of granulo- 

 blasts (eosinophilic myelocytes) are always in the immediate 

 neighborhood of some of the blood vessels pf the mucosa. When 

 the blood supply is increased as under inflammatory conditions 

 of any nature, as caused by some irritant, such as presence of 

 pathogenic organisms, the number of eosinophiles increases 

 correspondingly. The greater the blood supply, the greater 

 becomes the granulopoietic activity. It is very probable, there- 

 fore, that some agent in the blood stream (possibly in the plasma) 

 plays an important role in the process of granulopoiesis. It 

 may be suggested, therefore, that the underlying cause for ex- 

 cessive granulopoiesis is, then, the presence of some irritation 

 bringing about essentially inflammatory conditions, the direct 

 cause being some constituent of the blood stream (plasma?), 

 the exact nature and action of which influence is unknown. 



ERYTHROPOIESIS 



The possibility of erythropoiesis occurring in the mesenchyme 

 in various regions in the embryonic body has been noted by many 

 hematologists. 



Some of the earlier authors found in the subcutaneous connec- 

 tive tissue in some animals what they considered as intracellular 

 development of red corpuscles. (Schafer, '74; Ranvier, '74; 

 Le Boucq, '75.) This apparent intracellular development is 

 now usually considered as an instance of the reverse process, 

 atrophy of already formed vessels and breaking down of the con- 

 tained erythrocytes by phagocytosis. 



