COMPOUND 48/80 ON RAT 



small blood vessels with muscle coats until, by day thirty-two, many of these 

 vessels are surrounded by several layers of small, darkly-staining mast cells 

 (Fig. 38). 



Histamine. As Figures 39 and 40 indicate, continued injection of compound 

 48/80 largely suppresses the restoration of the tissue histamine, with the notable 



o— 



-• OMENTUM 

 -O MESENTERY 



DAYS 



Fig. 40 



Experiment as illustrated in Fig. 39. Histamine content of omentum (• •) 



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



J. Path. Bact. 69, 269.) 



exception of the subcutaneous connective tissue, in which a recovery of 50-60 

 per cent of normal is achieved by the thirty-second day. The omentum, too, 

 shows a somewhat lesser recovery of up to 40-50 per cent of normal, and here 

 we observed that when an extract of this omentum was tested on the cat's 

 blood pressure the initial fall due to histamine itself in the extract was followed 

 after a few seconds by a further fall, indicative of the presence of a histamine- 

 liberator. This may well be some of the compound 48 80 which had been used 

 in the experiment. 



Intra-arterial injection 



In this group only those animals were examined in which, judging by the 

 subsequent erythema of the ear on that side, the intra-arterial injection had 

 been successful. 



105 



