THE PARATHYROID GLANDS 549 



Petersen, Jobling, and Eggstein found that a progressive increase in 

 the non-coagulable nitrogen and proteose of the blood follows the operation 

 of thyroparathyroidectomy. The aniino-mtrogen is usually increased when 

 tetany is at its height. 



Inosinic Acid as the Toxic Agent. Greenwald (&) had previously 

 called attention to a marked retention of phosphorus after parathyroidec- 

 tomy in dogs, followed by a retention of sodium and potassium. It had been 

 shown that inorganic phosphates cannot give rise to tetany. Other phos- 

 phorus compounds were sought as the possible toxic agents, and inosinic 

 acid, one of the simplest of the nucleic acids, was investigated. An intra- 

 venous injection of inosinate of soda into a dog recently parathyroidecto- 

 mized gave rise to no symptoms of tetany ; therefore, it was concluded that 

 the toxic agent was not inosinic acid. The significance of the retention of 

 phosphorus remains unexplained. 



TTiymus Secretion as the Toxic Agent. Uhlenhuth (a) (&) (c) (d) 

 (e) (1917) showed that in thymus-fed salamander larvse tetany supervenes 

 similar to that in parathyroidectomized mammals ; when they develop para- 

 thyroids (at the time of metamorphosis) the tetany symptoms disappear. 

 The theory is advanced that the thymus produces substances which cause 

 tetany and secretes them into the body, from which they are removed by the 

 parathyroids. Removal of the latter would produce tetany. In subsequent 

 papers he elaborates this theory and presents additional evidence. 



Honeyman tested Uhlenhuth's theory that the thymus produces a 

 toxin which causes tetany in the absence of the parathyroid in certain sala- 

 mander larvae, when applied to the mammal. He removed the thymus 

 and the parathyroids at the same operation in the guinea pig. This did 

 not modify in any way the onset of symptoms of tetany. In the mammal, 

 then, it appears unlikely that the thymus secretes or contains any sub- 

 stance capable of producing tetany.* 



Physiology of Parathyroid Glands 



With regard to the functions of the parathyroid gland, it must be 

 admitted that our knowledge is still somewhat obscure. Various ideas 

 have been prevalent from time to time concerning this. 



One theory is that the secretions of the thyroid and parathyroid glands 

 have antagonistic actions on the central nervous system. The most obvious 

 effects of the removal of one or the other are the nervous symptoms which 

 follow in the one case depression, in the other excitation and it is 

 assumed that the autocoid produced by the parathyroid is a chalone 

 which according to Schafer may be termed provisionally parathyrin 



* Park has shown that complete thymus extirpation in the guinea pig is not 

 feasible. R. G. H. 



