EFFECTS OF THYROID ON PARAMAECIUM 



539 



One of these was maintained in the control medium, where it 

 continued four days without division and then slowly returned 

 to the control rate. Another was treated with a suspension of 

 Armour's thyroids (prepared by shaking up 1.5 mgm. in 2 cc. 

 boiled tap water and mixing with 2 cc. control hay infusion) 

 where it divided twice in the ensuing twenty-four hours. Two 

 of the resulting cells were returned to the control medium and 

 table 5 shows the comparative rates of division of the control, 

 thyroid and thyroid-control during the next few periods. A 

 thymus line started during this experiment using Armour's 

 thymus (prepared like the thyroid suspension) shows the same 

 rate of. division as the control. 



TABLE 6 



Race A. Experiment 6. Daily division rate averaged by five day periods 



Experiment A 6 was carried on as the race began to emerge 

 from the depression period. Thyroid prepared as in the pre- 

 vious experiment was used and after one period of slight effect 

 produced a very large increase in the division rate. 



TABLE 7 



Race A. Experiment 7. Daily division rate averaged by five day periods 



Experiment A 7 was performed during a time when the race 

 was at its highest division ra-te, and is rendered especiallj^ sig- 

 nificant by the fact that eight files were maintained for each line 

 instead of four. It will be noticed in this and other experiments 

 where the desiccated thymus was employed that the lines so 



