508 CHARLES E. STOCKAED AND E. M. VICABI 



sociation of the bulldog typed head, the bulldog thyroid pattern 

 and a pituitary closely following the microscopic anatomy for 

 the bulldog gland. 



Photomicrographs of pituitaries from three F 2 hybrid 

 brothers are shown in plate 96 (figs. 1, 3 and 4). These 

 pituitaries are of particular interest because of the differences 

 in their relative proportions and histologic structures in as- 

 sociation with the physical differences shown by the individual 

 members of this litter. 



Figure 1 gives a clearer picture of the general topography 

 and relative proportions of parts as seen in the bulldog 

 pituitary gland (fig. 2, pi. 95) than do either figures 3 or 4. 

 The dog from which this gland was taken, 1145 $ , was the 

 most bulldog-like member in his litter, as can be seen by 

 comparing figure 2 in plate 62 (p. 331) with others in the same 

 plate. The skull from this dog is third from the bulldog end in 

 the series of F 2 skulls in plate 57 (fig. 10). At the time of 

 his death this animal was a mature adult of 1^ years. A 

 section of the very abnormal thyroid gland may be seen in 

 plate 94 (fig. 3); the extreme activity of this thyroid has 

 already been pointed out. The follicles are small and of 

 irregular outline, and the cells in the walls of high columnar 

 epithelium are loaded with granules and vacuoles and are in 

 a most active state of secretion. However, the hyperactive 

 thyroid functioning within the constitution of this dog in- 

 duced no symptoms of hyperthyroidism unless one might 

 interpret an hereditary shyness as symptomatic, against which 

 we have much evidence to show that such shyness may be 

 as fully expressed by an animal with a hypoactive and col- 

 loidal thyroid. 



The pituitary of 1145 $ has a disproportionately large 

 spheroidal pars nervosa, which is covered by the pars inter- 

 media over its dorsal hemisphere only. The pars distalis is 

 limited in area and discoidal in shape. The pars tuberalis 

 does not completely surround the infundibular stalk and 

 many diverticula from the residual lumen extend into this 

 region. The groups and cords of cells in the pars distalis 



