INTRODUCTION 



in which this anticoagulant has been shown to find its way from tissues to 

 blood in the course of peptone or anaphylactic shock, and in no other species is 

 there a comparable prolongation of blood clotting during anaphylaxis. It is 

 true, as the Scandinavians had shown, that heparin can be extracted chemically 



ft V, 



Fig. 1 



Paraffin section dog liver, stained toluidine blue ( 192). The dark spots around the vein, in the 



portal tracts and scattered throughout the liver parenchyma are tissue mast cells. The dog is 



unique in having numerous mast cells in the substance of its liver. This finding has been 



turned to great advantage in solving the mystery of Ehrlich's mast cells. 



from the tissues of many species and in proportion to the original mast-cell 

 content, and that this extracted heparin, used in vivo or in vitro, proves to be 

 a highly efficient anticoagulant. Even so, we are not compelled to believe 

 either that a release of heparin is an essential feature of the anaphylactic 

 syndrome in general or even that the normal function of the mast cell is to 

 provide a constant slow release of anticoagulant to regulate blood clotting. 

 The dog is the exception, not the rule, with respect to the function of its mast 

 cells. 



On the other hand, there was no lack of evidence at that time concerning 

 the participation of histamine in anaphylactic shock in many species, though 



35 



