EFFECT OF THYROID ON DIVISION OF PARAMAECIUM 



299 



Diagram 1 To show ideal relations of sister lines of Paramaecia for comparing 

 difference in division rate produced by changes in environment. 



— ■ — = Control line = Sub-line for experiment 



with an equal quantity of boiled tap water. The quantity used 

 for each individual was four drops. 



The experimental lines were treated with the regular control 

 medium to which a small quantity of thyroid or thymus was 

 added. Whenever possible, glands from the same animal were 

 used. At first emulsions from fresh glands were employed, 

 later Armour's dried preparations. No attempt was made to 

 render the emulsions absolutely bacteria-free. In the following 

 accounts of the experiments, the emulsions used will be referred 

 to by the numbers under which they are here described. 



I. Thyroid Emulsion I and Thymus Emulsion I, were prepared from the 

 glands of ten rabbits killed and dissected April 6, kept in physiological salt solu- 

 tion twenty-four hours, macerated and mixed one part to two parts boiled tap 

 water. These emulsions were kept in a refrigerator at about 10°C. and were 

 used during period 7, in the proportion two drops to two drops 1-2 Standard Hay 

 Infusion. 



II. Thyroid Emulsion II and Thymus Emulsion II were prepared from the 

 glands of twenty rats killed and dissected April 13, kept in Ringer's Salt Solu- 

 tion twelve hours, macerated, ground, and mixed one part to two parts boiled tap 

 water. These emulsions wore kept in the refrigerator, and used during period 8 

 in the proportion two drops to two drops 1-2 S.H.I., and during periods 9 to 12, in 

 the proportion 1-4 drop to four drops 1-2 S.H.I. 



