histamine: normal tissues 



there is relatively much more histamine in the capsule of the liver than in the 

 rest of the organ, a paradox hardly to be explained except on the differences in 

 mast-cell content of the two tissues. 



This point was again emphasized when lung was examined in the same way. 

 Here it was necessary to remove the 'capsule', the visceral pleura, by the tedious 

 process of sharp dissection. The results show that the histamine content of 

 ox pleura, separated in this way, may actually exceed that of ox liver capsule 

 (Riley, 1953c). This may be due partly to the very thin nature of the pleura 

 and to the larger size of its numerous mast cells (Figs. 9 and 10 and Table V). 



Table V 



Histamine content (\xg.jg. tissue) and the relative mast-cell 

 content of the lung of different species 



Interesting as the above findings are in relating the histamine values to the 

 mast-cell contents of various organs and parts of organs in different species, 

 it might perhaps still be argued that the histamine contents are determined by 



Table VI 



Histamine content (y-g./g. tissue) and the relative mast-cell 

 content of organs of young and adult animals 



some cellular component not specifically demonstrated in the histological 

 preparations. Accordingly comparisons were made between the same tissue 

 at different periods in the life of the organism, taking advantage of the fact that 

 the mast-cell contents of many tissues also vary with the age of the individual. 



75 



