EFFECTS OF THYROID ON PARAMAECIUM 



541 



TABLE 10 



Race A. Summary of experiments. Average division rate per day 



Percentage increase produced by thyroid feeding, 65 per cent. 



viduals were less liable to death from slight environmental 

 changes. At all times the thyroid fed individuals were more 

 active, smaller and more transparent. Paramaecia treated with 

 thymus showed no such effects. In the course of these experi- 

 ments, some thyroid particles were stained with an alcoholic 

 solution of Congo red, the free color washed out in distilled water. 

 These prepared thyroid particles were then fed to Paramaecia 

 in the manner customary in these experiments. It was possible 

 to observe the formation of gastric vacuoles containing the pre- 

 pared thyroid and later to note the change from an acid to an 

 alkaline reaction shown by the indicator, exactly as described by 

 Metalnikow ('12). 



b. On the Brace. In the summer of 1914 attempts were made 

 to discover whether the effects produced by thyroid feeding 

 were due to the iodine content of the gland. It -was found that 

 iodine and iodine in combination with potassium iodide re- 

 sulted in depressing rather than raising the division rate even 

 when used in such small doses as 1/20,000,000. The experi- 

 mental data are given in table 11. 



In the fall of this year experiments were undertaken to dis- 

 cover whether the effect of the thyroid is unique among the in- 

 ternally secreting glands in producing an increased rate of di- 

 vision. In the first experiment cited, four lines were derived 

 from the control B' and treated for five periods of five days 



