GROWTH AND STRUCTURE OF HYPOPHYSIS IN RAT 837 



being 5.9 m in the newborn, 5.8 m at three weeks and 6.0 m at 

 ten weeks (sixty-seven days). In the three young rats held at 

 maintenance, the nuclear diameter has diminished, varying from 

 4.9 fx to 5.3 fjL. In the 2 older starved rats the corresponding 

 diameters are 5.3-5.5 ju. 



DIRECT MEASUREMENT OF NUCLEAR DIAMETERS 



Owing to the imperfections of the volumetric method pre- 

 viously considered, and to the small number of cases to which 

 it was applied, the results should be considered as only approxi- 

 mate and not final. So far as the nuclear diameters are con- 

 cerned, however, the results have been controlled by a totally 

 different method, that of direct measurement of the nuclear 

 diameters with a filar micrometer eyepiece. Where the nuclear 

 diameters are unequal (slightly ellipsoidal forms are frequent), 

 the average of the longer and shorter diameters was taken. 

 Nuclei apparently cut near the edge, so as to leave the maximum 

 extent outside the section, were avoided so far as possible. The 

 average (and range) for 100 nuclei in each case is shown in table 4. 



The results of these direct nuclear measurements are more 

 uniform, and in closer agreement with those of the volumetric 

 method, than might be expected. This will appear upon a com- 



Fig. 2 A small portion of the pars anterior of the hypophysis in a normal rat 

 at three weeks (J 1.2). Most of the cells are of the faintly basophilic type. Some 

 eosinophilic cells are indicated by darker staining (two near the upper margin of 

 the figure). A few chromophobic cells are shown, a group of four near the right 

 margin. Zenker fixation; haematoxylin stain. Drawn with the aid of a camera 

 hicida. X 950. 



Fig. 3 A small portion of the pars anterior of the hypophysis in a young rat 

 (S 5.12) held at maintenance from age of three to ten weeks. The inanition 

 effect is very marked, with hyperemia and atrophy of the parenchyma. Cyto- 

 plasm diminished in amount, sparsely granular and filled with coarse vacuoles 

 whicli in places coalesce to form irregular spaces. Nuclei hyperchromatic, in 

 various stages of pj'cnosis. Zenker fixation; haematoxylin-eosin stain. Drawn 

 with the aid of a camera lucida. X 950. 



Fig. 4 A small portion of the pars anterior of the hypophysis in a normal rat 

 aged ten weeks (St 47.5). This represents the typical adult structure. Most of 

 the cells are of the weakly basophilic type. Several eosinophiles are indicated, 

 the more strongly acidophilic having a darker color. Zenker fixation; haema- 

 toxylin-eosin stain. Drawn with the aid of a camera lucida. X 950. 



THE AMERICAN JOLKNAL OF A.VATOMY, VOL. 21, NO. 2 



