478 CHARLES R. STOCKARD AND E. M. VICARI 



the so-called principal cell type. Scattered irregularly among 

 these are a few cells which are somewhat larger, granular 

 and bluish staining. 



The exact microscopic patterns of all parathyroid bodies 

 from one individual are not necessarily the same. One para- 

 thyroid may show embryonic arrests with branchial epithelium 

 and cystic formations, while others from the same thyroid 

 may be fully differentiated with a typically normal histology. 

 Nonidez and Goodale have found that in cases of experi- 

 mental rickets in chickens one parathyroid body may be only 

 slightly hypertrophied, while another shows advanced de- 

 generation, and a third complete atrophy. From such facts 

 it is quite obvious that modifications in the histology of one 

 or more of the parathyroid bodies cannot very well be as- 

 sociated in a consistent manner with the special types and 

 breeds of dogs. However, these glands are so definitely con- 

 cerned with calcium metabolism, and through this with the 

 growth and quality of bone in the mammalian body, that 

 we are justified in seeking any possible clue which might 

 relate them to either overgrowth of stature or dwarf tenden- 

 cies, or possibly to the various distortions in form and type 

 which result from chondrodystrophy and other skeletal growth 

 disturbances. 



The role of the parathyroid bodies in mineral metabolism, 

 and particularly calcium metabolism, has been clearly estab- 

 lished through studies of human and experimental tetany. 

 The palliative and therapeutic effects of calcium on this 

 condition were shown long ago by MacCallum and Voegtlin 

 ('09), Luckhardt and Goldberg ('23) and many others. And 

 finally, the hormone from the parathyroids was isolated by 

 Collip from the glands of calves in 1925, and was shown 

 to give direct relief in symptoms of tetany in man and 

 to maintain a parathyroidless animal in a normal state. 



The causal relation of the parathyroids to tetany is so 

 complete, and tetany would seem to be so simple an ex- 

 pression, that one might suppose it an easy task to associate 

 a definite histopathology of the glands with this condition. 



