630 LEWELLYS F. BAKKEK 



been repeated in dogs and in rabbits by Massaglia (1911) and by Cleret 

 and Gley (rf) (&) (1911), but the tetany could not thus be prevented. 



Thymus Gland 



On account of the laryngospasm that occurs in tetany, in rickets, and, 

 sometimes, in status thymicus, the idea of a relationship of the thymus 

 gland to tetany and to insufficiency of the parathyroid glands has arisen. 



The most interesting experimental work in this connection is that of 

 Uhlenhuth (c) (d) (e) (1918-19) done at the Kockefeller Institute in New 

 York. This observer fed larvae of the salamander Amblystoma opacum on 

 thymus gland derived from the calf. The members of one series of half a 

 dozen larva?, otherwise untreated, all developed tetany with convulsions., 

 which ceased as metamorphosis approached. After metamorphosis, all the 

 larvae of this series were free from tetany, though the limbs and feet re- 

 mained deformed and contracted and the muscles were permanently para- 

 lyzed. A second series of larvae was kept in a solution of calcium lactate 

 and fed on thymus gland. Tetany was less marked than in the first series, 

 but the residual paralyses and deformities were quite as marked; more- 

 over, several weeks after metamorphosis, tetany appeared in members of 

 this series. A third series of the larvae was kept in a solution of mag- 

 nesium lactate during the thymus feeding. These larvae behaved like 

 those in the second series, except that the tetany was still less marked dur- 

 ing the larval period. 



Further proof of the antagonism that he believes to exist between the 

 thymus and the parathyroids has been brought by Uhlenhuth (e) in a sec- 

 ond paper (1919). It seems that the larvae of Amblystoma opacum have no 

 parathyroids until metamorphosis occurs. If they be fed on calf's thymus 

 while in the larval state, tetany, as has been mentioned above, develops. 

 Uhlenhuth found, however, that after the development of their parathy- 

 roids, three of the animals fed on thymus gland were able to subsist for at 

 least seven months without the appearance of tetany. 



Uhlenhuth believes that the parathyroid glands are, in the sala- 

 mander, as they are in man, important in the prevention of tetany. But, 

 in addition to the parathyroids, the salamander, he asserts, possesses an- 

 other mechanism that, during the larval period, prevents the development 

 of the tetany that would otherwise result from the toxic effect of the larval 

 animal's own thymus gland. In Amblystoma opacum and in Amblystoma 

 maculatum this mechanism suffices for the prevention of tetany due to 

 auto-intoxication by the animal's own thymus; whereas in Amblystoma 

 tigrinum this same mechanism is capable of preventing tetany, even when, 

 to autothymo-intoxication is added the poison of calf's thymus fed to it. 



Uhlenhuth points out that, if the thymus be regarded as the organ the 

 activity of which is responsible in hypoparathyroid states for the appear- 



