224 Cc. M. JACKSON 
The method used for the volumetric determinations is a modi- 
fication of Hammar’s paper method, as described in my work on 
the hypophysis (Jackson,’17). The outlines of the magnified sec- 
tions are projected and drawn upon ‘American linen record’ paper 
(sheets 18 x 23 inches, 36 lbs. per ream) by means of an Edinger 
projection apparatus. Four samples, each 5 cm. square, are 
weighed from each sheet, and the area corresponding to each gram 
of paper determined. The structures whose volume is to be 
determined are then cut out and weighed, and the corresponding 
area calculated. This magnified area is then reduced to actual 
area (dividing by the square of the magnification). Multiply- 
ing by the actual thickness of the sections now gives the actual 
volume of the parts concerned. For determining the volumes of 
cortex and medulla (table 2) it was not considered necessary to 
draw every section. Enough were taken to make a total of at 
least fifty drawings for each suprarenal. This required every 
fourth section for some of the smaller glands, but fewer for the 
larger glands, some of the largest requiring only every sixteenth 
section. A magnification of 75 diameters was used for the cortex 
and medulla. 
As was found in the hypophysis, the volumes obtained (in 
cubic centimeters) are usually considerably less than half the 
corresponding fresh weight of the gland (in grams). The differ- 
ence is due: 1) to the density of the gland; 2) to the fibrous cap- 
sule and attached extracapsular tissue, weighed but not measured 
(forming about 11 per cent of the gland in the dog, according to 
Flint’s data), and 3) to the great shrinkage due to the process of 
fixation, dehydration, and embedding in paraffin. 
For determining the relative volumes of parenchyma and stroma 
(including blood-vessels), a higher magnification was required. 
A Leitz ocular no. 4 and objective no. 7a were used, with large © 
Spencer camera lucida, giving at table level a magnification of 
about 500 diameters. As it is impracticable to measure the en- 
tire gland in this way, typical areas are selected and drawn from 
the various regions of the cortex and medulla, outlining merely 
the areas of parenchyma and vascular stroma in a given plane. 
These areas are then cut out of the paper and weighed. Since 
