326 C. M. JACKSON 



Tlic volumes of the various ]){irts (lobes) of the hypophysis 

 were determmed by a method similar to that used Ijy Hanimar 

 ('14) for tlie thymus. The outUnes of the sections, magnified 

 75 diameters, were projected upon '^\merican 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, 

 were weighed from each sheet, and the area corresponding to 

 each gram of paper determined. The various lobes as outlined 

 were then cut out and weighed, and the corresponding areas 

 calculated. This magnified area was then reduced to actual 

 area and multiplied by the thickness of the sections, giving the 

 actual volume for each lobe. By trial it was found to be un- 

 necessary to draw every section, about 50 sections taken at 

 equal intervals (every fifth to tenth section) being found to give 

 nearly identical results. 



On comparing the original weight of the hypophysis with the 

 volume obtained by the preceding method, there is apparently a 

 marked discrepancy, the volume (in cubic centimeters) being less 

 than half the weight (in grams) (table 2). The difference is due: 

 (1) to the density of the gland; (2) to the capsule and extra- 

 capsular structures attached, which were weighed but not in- 

 cluded in the volmne measured; (3) to the great shrinkage 

 resulting from the process of fixation, dehydration and embedding 

 in paraffin. This process alone would probably account for a 

 shrinkage of nearly one-third in volume. 



For the pars anterior (distalis), a plan similar to that above 

 given for the lobes was followed to determine the relative volumes 

 of the vascular stroma and the parenchyma; and of the nuclei 

 and cytoplasm in the parenchyma. For this piu'j^ose, a higher 

 magnification (Zeiss 2 mm. apochromat with compensating ocu- 

 lar 6, giving magnification of 1420 diameters at table level) was 

 used. A typical field was chosen, and as large an area as possible 

 drawn, with the aid of a Spencer camera lucida. It is important 

 that the section drawn represent as nearly as possible a true 

 optical plane, and therefore no change of focus during the draw- 

 ing is permissible. If this is not carefully done, there will be a 

 tendency to draw the nuclei too large, since their maximum 



