MAST CELLS AND HISTAMINE IN SKIN 



counted in the toluidine blue preparation at a magnification of 120 diameters 

 using a binocular Watson microscope of standard tube length, eye-piece X 8 

 and objective x 16. Ten fields, chosen at random, were counted for each tissue 

 layer, the results being expressed as "mast cells per microscope field'. For the 

 pharmacological assays, weighed portions of tissue adjacent to those selected 



Table XXIII 



Regional variations in histamine and mast-cell 

 contents in hog ear 



Upper Surface 



Base 



Tip 



Lower Surface 



Histamine values are expressed as micrograms per gram; corresponding mast-cell contents (in 

 parentheses) are average figures for 10 standard microscope fields, counted from vertical paraffin 

 sections. There is a positive correlation between histamine and mast cells in each region, and a 

 gradient in both which increases towards the tip of the ear. 



Table XXIV 



Histamine contents and mast-cell values for ox ear 



Upper Surface 



Base 



Tip 



Lower Surface 



As in hog ear, the values both for histamine and for mast cells (in parentheses) are higher in the 

 upper than in the lower skin and increase towards the tip of the ear where maximal concentrations 

 are found. The few mast cells in the perichondrium have not been recorded. 



for histological examination were immersed as soon as possible in 10 per cent 

 solution of trichloracetic acid and were later extracted and assayed for histamine, 

 as in previous work (Riley and West, 1953), using either the guinea pig ileum 

 preparation or the blood pressure of the atropinized cat. Histamine values 

 are expressed as micrograms of histamine base per gram of fresh tissue. 



Results. Tables XXIII and XXIV illustrate the findings for histamine 

 and mast cells in the ear of hog and ox. In both species there is a close 



K 



145 



