GENETIC TYPE AND THE ENDOCRINES 519 



glands. The nuclei in these masses are closely packed in all 

 directions, and while in thin sections only one or two levels 

 of principal cell nuclei can be seen, several layers may be 

 detected in these congested cell groups. A definite interpreta- 

 tion of such arrangements is difficult to offer. It is probable, 

 but not entirely certain, that the cellular masses are to be 

 classed as bluish staining- rather than principal cell types. A 

 study of the history and condition of the animal from which 

 this section was derived does not furnish any valuable sug- 

 gestions. This dog was killed as a young adult of 2 years, 

 and the fresh glands were carefully fixed for sectioning 

 at the same time as those from the brother, 1312 3, which 

 furnished the parathyroid section in figure 6. The thyroids 

 from these two animals, shown in plate 93 (figs. 5 and 6), 

 were both fairly well fixed and are quite similar in pattern. 

 Such dark bluish masses of cells in the parathyroid have been 

 seen by other authors and are not to be dismissed simply 

 as artefact due to the technique. 



The F 2 hybrid 1313 $ was a short legged bassethound-like 

 animal weighing 20 kilograms and with very little thymus 

 glandular tissue. The brother, 1312 $ , weighed more than 

 30 kilograms and was of St. Bernard type with long legs. 

 In his case an unusually large mass of glandular thymic 

 tissue was present. In these hybrids, an acidophilic condition 

 of the pituitary is associated with an enlarged thymus. The 

 parathyroids from these two hybrid brothers are very dif- 

 ferent, and yet it is impossible to satisfactorily associate their 

 histologic pictures with the peculiar type differences between 

 them. 



Photomicrographs of three other F 2 bassethound-bulldog 

 parathyroid glands at slightly higher magnification are shown 

 in plate 98. These sections illustrate in a more pronounced 

 manner several of the conditions mentioned above. Figure 

 1, from 918 2 , shows the strong expression of circles and 

 whorls formed by excessive twisting of the cellular cords 

 about the capillaries. The more usual arrangement of serpen- 

 tine cords of double rows of cells is less abundant. The 



