408 CHARLES It. STOCKAKD AND E. M. VICAKI 



uniformly normal canine proportions with a low degree of 

 variability in the relative sizes of all their parts. The range 

 in thyroid size for the great Dane is only as 1:1.5, while in 

 the bulldog it is four times greater, or as 1 :6. 



The question now arises whether relative amounts of thyroid 

 tissue might not differ widely enough between two breeds to 

 indicate some bearing on breed differentiation. In attempting 

 to answer this question, one must assume that relative thyroid 

 proportions are probably of no breed significance unless the 

 difference between two breeds is very much greater than 

 the differences among similar members of a single breed. 

 The six breeds already considered for individual thyroid 

 variations are widely different types and serve admirably for 

 these interbreed comparisons. The average relative sizes of 

 thyroid to kilogram of body weight for each breed may be 

 determined from the individual records in the charts, and 

 these range as follows : six adult bassethounds, 267 milligrams ; 

 seven dachshunds, 224 milligrams ; thirteen English bulldogs, 

 163 milligrams; six Boston terriers, 140 milligrams; six great 

 Danes, 93 milligrams; and ten St. Bernards, 85 milligrams. 

 In this series of averages— 267-224-163-140-93-85— the high- 

 est value is three times greater than the smallest, that is, 

 the average bassethound has about three times more thyroid 

 material per kilogram of body weight than does the average 

 St. Bernard. The individual charts also show that the lowest 

 bassethound record of 160 milligrams is larger than the high- 

 est individual St. Bernard record of 125 milligrams. There 

 is no overlapping between these two breeds. The lowest bas- 

 sethound also has relatively more thyroid tissue than the 

 highest recorded great Dane. There is also no overlapping 

 in relative thyroid size between the dachshund and great 

 Dane or St. Bernard. But the individual records of the 

 bassethound, dachshund, bulldog, and Boston terrier do show 

 considerable overlapping. This overlapping among breeds so 

 highly contrasted in size and type is another strong indica- 

 tion that the relative quantity of thyroid tissue is of no 

 significance in the determination of structural type or pattern. 



