COMPOUND 48/80 ON RAT 



histamine, whereas the subcutaneous connective tissue is almost back to normal. 

 By day thirty-two recovery is complete in all four regions studied histologically. 



' Chronic dosage ' experiment 



It is necessary here to describe only the histological appearances from day 

 five onwards, since this experiment was in fact an extension of the subacute 



Fig. 38 



' Chronic dosage 'experiment. Subcutaneous tissue at day thirty-two. Despite continued 

 intraperitoneal injection of compound 48/80 (1 mg./day), numerous small mast cells 

 are now appearing around the blood vessels. There was a corresponding return of the 

 tissue histamine. Toluidine bli-e ( ;<220). (Riley and West (1955), ./. Path. Bad. 69, 269.) 



(five-day) experiment, daily doses of histamine-liberator being administered 

 thereafter for a further twenty-six days. It is of pharmacological interest that 

 during this period there was no mortality despite the repeated injection of 

 even 1 mg., thus confirming the low intrinsic toxicity claimed for compound 

 48/80. 



Mast cells. Throughout the period of injection there is little evidence of 

 recovery of mast cells in either mesentery or omentum. In the mesentery no 

 perivascular mast cells are to be seen, and the only scattered ones are in relation 

 to patches of organizing exudate; their granules are small and pale. In con- 

 trast, macrophages laden with debris are very common, being especially 

 numerous in the omentum. Characteristic of the omentum, too, in this group 



103 



