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WALDO SHUMWAY 



treated in the same way except that thymus was substituted 

 for thyroid. The table above shows the average division rate 

 for each Une during the periods in which the experiment was 

 continued. As is seen, the average for D is always greater 

 than for A, while E does not show this increase. The F line, 

 started from the D line after fifteen days of thyroid treatment 

 and kept thereafter in control medium, shows a return to the 

 average rate of A. 



Experiment II. April 24 to May 8, 1913. 



Ave7-age Division Rate 



J 



(thymus) 



A 



(CONTROL) 



D 



(thyroid) 



1.00 



1.55 

 1.45 

 2.20 



3.60 

 2.80 

 3.15 



This experiment was commenced during Experiment I to 

 discover whether the effects observed in the thyroid treated 

 individuals would be produced in other individuals of the same 

 race. An individual was selected from the A line, and allowed 

 to divide until there were twelve cells of the same generation. 

 Four of these were allowed to continue in the control medium, 

 forming line G, four were treated with Thyroid III (H), and four 

 with Thymus III (J). The table shows the division rate for the 

 three ensuing periods. For purposes of comparison, I have added 

 the averages given by the control and thyroid lines of the pre- 

 ceding experiment for the same periods. This experiment con- 

 firms the results of Experiment I. 



Experiment III. June 28 to July 2, 1913. 



Average Division Rale 



This experiment was performed at Woods Hole. After the 

 trip from New York and the change to Woods Hole tap water 



