THE MAST CELLS 



darkly-stained material similar to the remnants around the mesenteric vessels; 

 these cells are more suggestive of macrophages containing debris released from 

 other cells than of mast cells in course of disruption. 



One feature common to all regions in which mast cells are disappearing is 

 the progressive swelling and increased basophilia of the connective-tissue cells 

 in the adventitia of the small blood vessels, a process which seems to extend 

 outwards from the vessels and ultimately to involve all the loose mesenchyme. 



4 



i 



. 



A 



Fig. 31 



' Acute dosage ' experiment. Mesentery three hours after intraperitoneal injection of com- 

 pound 48/80, showing shattered mast cells and early swelling and increased basophilia of 

 the adventitial cells. Very little histamine remained in this tissue. Toluidine blue ( 580). 

 (Riley and West (1955), /. Path. Bad. 69, 269.) 



As might be expected, the disruptive effects on the mast cells in regions 

 remote from the injection site are less than in the peritoneal cavity itself. In 

 the subcutaneous connective tissue the changes are often patchy in distribution, 

 ranging from swelling and 'degranulation' of intact mast cells to the complete 

 disruption of the cells and the scattering around them of pale orthochromatic 

 granules. The nuclei of the swollen cells are themselves swollen and rather 

 more basophil than normal. This general description of conditions in the 

 subcutaneous connective tissue applies also to the ears except that more of 

 the mast cells survive the early stages of the disruptive process. 



By day four, the main histological feature in the 'acute dosage' experiment is 

 the apparently complete restoration of the mast-cell picture in the subcutaneous 



96 



