THE MAST CELLS 



the mesentery a wave of such cells can sometimes be observed spreading over 

 a peritoneal window from the fatty fringe which surrounds it; and within the 

 fatty fringe itself small attenuated mast cells lie closely applied to the septa 

 of fat cells and apparently arising from them. The fat cells in mesentery and 

 omentum thus come to have a signet-ring appearance (Fig. 35). Gradually 



DAYS 



Fig. 37 



Experiment as illustrated in Fig. 36. Histamine content of omentum (• •) 



and mesentery (O O) shown in the two tracings. (Riley and West (1955), 



J. Path. Bact. 69, 269.) 



all these small cells increase in size and fill with granules until, by day eighteen, 

 the two types of mast cell (refilled 'ghost' cells and hypertrophied small cells) 

 can no longer be distinguished. Even the accentuated vascular pattern of 

 the peritoneum has now returned to normal, leaving here and there clumps of 

 organizing fibroblasts embedded in a metachromatic ground substance and 

 surrounded by small dark mast cells. 



Histamine. The chief difference in the histamine pattern between the 'acute 

 dosage' and 'subacute dosage' experiments is that in the latter the precipitous 

 fall at the beginning of the experiment (affecting alike all tissues studied) is 

 followed by a slower rate of recovery, especially in the skin of the ear (Figs. 

 36 and 37). Thus at day eighteen the ears show only 50 per cent restoration of 



102 



