34 TETANY-PRODUCING SUBSTANCE IN THYMUS GLAND 



recently published feeding experiments performed on tadpoles of 

 frogs which seem to prove that the feeding of such larvae with thymus 

 gland of mammals has no influence whatever on growth. The 

 writer's^ own experiments on salamanders demonstrate clearly that 

 during the larval period of these animals, thymus when given as food 

 may considerably change the rate of growth, but that this is not due 

 to a specific influence of that gland upon growth. 



It is, therefore, of interest that we are able to show that the tetany 

 produced in thymus-fed salamander larvae is not due to a deficiency 

 in the thymus of one or several substances, but is due to the presence 

 in the thymus of a specific tetany-producing substance. 



EXPERIMENTAL. 



'If tetany in salamander larvae fed on thymus is due to the absence 

 from the thymus of one or more substances, it is clear that the addition 

 of a sufficient amount of normal food to the thymus diet should pre- 

 vent the development of tetanic convulsions. It was found, however, 

 that this is not the case. 



Thirty larvae of the species Amby stoma maculatum — from the same 

 mother and of the same age — were fed on thymus from about the 

 5th week after hatching. The larvae developed tetany very soon; 

 convulsions were noticed as early as 15 days after the first thymus 

 meal. At the end of the 3rd week, the series was divided into two 

 lots, each containing fifteen individuals. One group was fed on 

 thymus exclusively, the other one was fed alternately one day on 

 thymus and one day on earthworms, the latter constituting a com- 

 plete diet in the case of the salam.anders. 



The result of this experiment was that tetany is not stopped by 

 the addition of a sufficient amount of complete diet, but on the con- 

 trary developed still further towards a maximum. Therefore, the 

 tetanic convulsions resulting from thymus feeding are not due to a 

 deficiency in the diet but must be due to a specific tetany-producing 

 substance contained in the th^iiius gland. 



It was also noticed that in the mixed food series tke tetany period 

 was shorter than in the thymus series and that the percentage of ani- 



^ Uhlenhuth, Proc. Soc. Exp. Biol, and Med., 1917, .xv, 37. 



