EDUARD UHLENHUTH 25 



Relation between Tetany and Development. 



Tetany cannot be produced by thymus feeding before a certain 

 developmental stage is reached by the larva; namely, that at which 

 probably the secretive power of the animal's own thymus glands is 

 estabhshed. This stage of development corresponds to that of the 

 full development of the toes of the larvas. 



Six larvae of Amhy stoma opacum iopacum, 1917, B), from North 

 Carolina, hatched in the laboratory from eggs of the same female, 

 were kept at approximately 25°C. and fed on calf's thymus from the 

 19th day after hatching. The animals were tested for tetany regu- 

 larly on a definite day every week, for the purpose of recording the 

 percentage of animals suffering from tetany; clonic convulsions of the 

 entire body as well as of the hind portion only were considered as indi- 

 cation of tetany. No animal suffered from tetany when examined 

 the first time after the commencement of the thymus feeding. With 

 the progress of development (as indicated by the development of the 

 toes) the percentage of animals suffering from tetanic convulsions in- 

 creased and reached a first maximum at the time when all toes were 

 developed. No animal had convulsions until all the toes of the fore 

 legs and at least the third toe of the hind limbs were developed. 



In a second series of experiments, with eight Ambystoma opacum 

 larvas (opacum, 1916, B) hatched from eggs of the same female and 

 kept at approximately 25°C., thymus feeding was started on the 14th 

 day after hatching. None of the larvae of this series showed any signs 

 of tetany before the full number of toes had developed. In a third 

 series {Ambystoma opacum, 1916, D) consisting of eight larvae from 

 eggs of the same female and of the same age as the larvae of the previous 

 series, this becomes still more evident. Though the larvae of Series D, 

 1916, were fed on thymus simultaneously with Series B, 1916, con- 

 vulsions developed 4 weeks later than in Series B, 1916. Develop- 

 ment was retarded by keeping the larvae in low temperature (15°C. 

 approximately) . 



In Ambystoma maculatum similar results were obtained. In one 

 instance {Ambystoma punctatum, Series K, 1917) six larvae, all hatched 

 from eggs of the same female and kept at approximately 25°C., were 

 fed on thymus exclusively from the 13th day after hatching. The first 

 acute attacks were observed 5 weeks after hatching. 



