426 CHARLES R. STOCKARD AND K. M. VICAI.'I 



4 in plate 81 illustrates the normal histology of the foxhound 

 thyroid. The follicles are large and fairly regular in outline 

 and the epithelium is of a moderately active type. The fixed 

 colloid tends to be hard and slightly brittle. Nests of para- 

 follicular epithelial cells are seen lying in the sparse extra- 

 follicular tissue. These cells have recently been discussed by 

 Nonidez ('32 a, '32 b, '33), in our laboratory, and by other 

 investigators. Their relative amounts are quite characteristic 

 in certain breeds. The foxhound thyroid is similar in its 

 histology to the normal human and other mammalian thyroids. 



Figure 3 (pi. 82) illustrates the German shepherd thyroid. 

 Again the follicles are large and regular in outline, but the 

 epithelium is higher and more active than in the foxhound, 

 as is indicated by the secretion droplets. Thyroid sections 

 from two other German shepherd dogs are shown, for com- 

 parative purposes, in plate 83. The colloid of the somewhat 

 more active shepherd gland is not so hard as in the foxhound 

 and is less brittle. In general there are fewer parafollicular 

 cells in the shepherd than in the foxhound thyroid. There 

 are only small amounts of extrafollicular tissue in both these 

 thyroids. 



Most decided deviations from this normal pattern of thyroid 

 histology are shown by the entire group of dog breeds possess- 

 ing short skulls of the bulldog type. The general nature of 

 the thyroid distortion in all the bulldog-like breeds is some- 

 what the same, yet wide specific differences are to be found 

 among them. 



Figure 1 in plate 81 is a highly characteristic and typical 

 section of the English bulldog thyroid. We have studied 

 thyroids from thirteen bulldogs, seven males and six females, 

 and the type of histologic distortion in all these glands is 

 remarkably consistent. One familiar with the histologic pic- 

 ture of its thyroid would undoubtedly feel that the English 

 bulldog can be recognized almost as certainly from it as from 

 the characteristic pattern of the head. Both characters vary 

 about equally. Yet we must not be misunderstood as presum- 

 ing at this time a direct causal relation between the two. 



