414 CHARLES 1,'. STOCKARD AND E. M. VICARI 



the histologic quality upon which its function depends for 

 the possible relationship between thyroid activity and bodily 

 type. However, a study of the differences in relative quantity 

 of gland was necessary in order to know what, if any, effects 

 size might exert before attempting to interpret the meaning 

 of differences in histologic quality, and we now know that 

 a small amount of gland seems fully capable of supplying 

 the necessary amount of hormones, and only the quality of 

 the gland would seem to be of prime importance. 



Gross Relative Sizes of the Pituitary Glands in Contrasted 

 Breed Types and Their Hybrids 



The relative amount of pituitary gland in milligrams per 

 kilogram of body weight was estimated for the same six pure 

 breeds for which the gross thyroid relations were discussed. 

 An accurate measurement of volume and weight is more diffi- 

 cult to obtain for the pituitary than for the thyroid. In re- 

 moving the pituitary from the base of the brain it is usually 

 preferable to include with it a small amount of brain tissue 

 in order to make sure of including the entire pars tuberalis 

 and the infundibular stalk. The histologic and cytologic na- 

 ture of this gland is known to play so important a role in 

 the growth and structural development of the individual that 

 there could be no sacrifice of histologic material in favor of 

 more accurate gross proportions. For such reasons, variable 

 small amounts of brain tissue are frequently included when 

 calculating pituitary size; but definite effort has been made 

 to control this extraneous tissue, and we are quite certain 

 that the possible error is irregularly distributed throughout 

 the records without advantage to any one group. The ad- 

 hering membranes, often difficult to remove from the human 

 pituitary, are not involved in the dog. 



Text-figures 82, 83 and 84 indicate the relative sizes of 

 pituitary gland for the same groups of dogs which furnished 

 the thyroid records already examined in text-figures 7i), SO 

 and Si. The individual mass of pituitary, as compared with 



