COMPOUND 48/80 ON RAT 



Recovery is remarkably rapid once the injections have ceased, despite the 

 extent to which the mast cells appear to have been damaged by the repeated 

 injections. In as short a time as four days (day nine of the experiment), there 

 is substantial restoration of the mast-cell pattern in the skin of the ear and even 

 more so in the subcutaneous connective tissue. It is noteworthy that these are 



so 



40 



HIST. 



30- 



20 



10 



O O SUBCUTIS 



20 25 



30 



35 



DAYS 



Fig. 36 



' Subacute dosage * experiment. Effect of 48/80 (given over five days) on the 



histamine content of subcutaneous connective tissue (O O) and ears 



(• • of rats. Histamine content expressed in ^g./g. tissue in the upper 



tracings and in percentage of normal values in the lower tracings. Note the 



slower recovery of tissue histamine, particularly in the ears. (Riley and West 



(1955), J. Path. Bact. 69, 269.) 



almost all large cells, though poor in granules. Such large 'ghost' mast cells 

 appear occasionally in the peritoneum, especially near vessels of intermediate 

 size. In addition, however, both in the mesentery and in the omentum numerous 

 very small mast cells, each containing a few minute granules, are now appearing 

 in the adventitia among similar oat-shaped but non-granular cells which lie 

 with their long axes parallel to the vessel wall. 



By day eleven these small new cells are common throughout the peritoneum 

 and are seen particularly clearly in the delicate connective-tissue framework of 

 the omentum, where they are not obscured by other structures (Fig. 35). In 



101 



