EDUAED UHLENHUTH ' 319 



in all the untreated thymus-fed animals. This surprising difference 

 has not found so far any explanation and will not be considered 

 in the present article, detailed discussion being reserved until further 

 experiments upon this phenomenon are available. 



///. Thymus-Fed Series, Kept in Mg Lactate {Fig. 1, Curve III). — 

 Seven larvae of Amby stoma opacum were used; one of them died soon 

 after the experiment had been started. 8 days after the beginning 

 of the thymus feeding and before tetanic convulsions had made their 

 appearance, the larvce were transferred to a 1/1250 m solution of Mg 

 lactate in tap water. By this concentration tetanic convulsions were 

 suppressed until the end of the 7th week; at this time one larva had 

 convulsions. But even though the concentration had been lowered 

 to only 1/2500 m, no further convulsions occurred until the 10th 

 week; the concentration was increased to 1/625 m, upon which the 

 curve fell immediately to zero. The concentration was further in- 

 creased to 1/500 m; only one larva developed tetanic convulsions of 

 the posterior portion of the body, and no further attacks were observed 

 among the larv£e, the rise of the curve at the end of the 18th week 

 being due to tetany of a metamorphosed animal. 



In this series the Mg lactate had a distinct and very definite influ- 

 ence upon the frequency and severity of the muscular convulsions; 

 not only is the curve running far lower than in the untreated thymus- 

 fed series, but it is also lower than in the Ca series. Furtherrnore, 

 three of six larvae had no muscular convulsions during the larval 

 period. Evidently the effect of the Mg lactate in suppressing the 

 muscular convulsions during tetany is far greater than that of the 

 Ca lactate, when used in the concentrations employed in these 

 experiments. 



This influence of the Mg lactate upon the convulsions of the 

 muscles, however, does not mean that Mg is able to suppress tetany, 

 for the other symptoms of tetany, i.e. paralysis of the muscles and 

 deformation of the extremities and of the body, develop and to the 

 same degree as in non-treated thymus-fed larvae. 



Concerning the metamorphosed animals the same phenomenon is 

 observed as in the Ca series. A number of weeks after the animals 

 had metamorphosed and were set on moist filter paper without being 

 exposed longer to Mg lactate, they began to suffer again from tetanic 



