Chemical Papers. 47 



nine days. Ax continued dividing slowly until the eleventh day, 

 when it ceased dividing, and died on the twenty-second day. 

 During this time the check cultures, A and C, had divided eighteen 

 and six times, respectively. 



The check culture C shows a low state of vitality, which accounts 

 for the early death of Cx. 



For comparison, we have in the NaCl culture Ax eight genera- 

 tions, as against eighteen generations of the hay check culture A ; 

 and in NaCl culture Cx we have two generations, against six of the 

 hay check culture C. 



This experiment shows conclusively that continued use of NaCl 

 retards division and finally produces death. It may be safely in- 

 ferred that the continued use of any chemical produces a decrease 

 in the vitality. 



I have also started a series of experiments to determine the effect 

 of the stimulation of an individual on the race. The chemicals 

 employed are one per cent. NaCl, one per cent. MgCl-i, and a weak 

 solution of curare. The NaCl and curare cultures are now twenty- 

 five days old and the MgCl2 culture twenty-one days old. The 

 NaCl and curare cultures were taken from the same generation of 

 hay culture C, while the MgClo culture is from D. Each culture 

 has been stimulated twice by its respective chemical for periods 

 varying from twenty to twenty-five minutes. 



Up to the present time the NaCl and curare cultures show no 

 decided variations from the check cultures. The MgCb culture 

 has shown a decided decrease in vitalty. The check culture has 

 passed through seventeen generations while the chemically stimu- 

 lated one has had only twelve generations. This shows that some 

 chemicals decrease the vitality of the race, even when given in dilute 

 solutions and only for a few minutes at a time. 



Calkins has succeeded in renewing the vitality of paramcecium 

 by chemical stimulation when in periods of depression. He gen- 

 erally uses extracts from animal tissues, such as the brain, liver, and 

 pancreas. Beef extract has been tested perhaps the most. In my 

 own cultures, when there has heeli no division for six days, and the 

 animals begin to show signs of dying, by stimulating with weak 

 Liebig's beef extract the cultures have been restored to their nor- 

 mal vitality. Beef extract is not a food but a stimulant. Calkins 

 shows that weak alcohol with continued use increases the division 

 rate and tends to offset periods of depression. Also, that continued 

 use of strychnine slightly increases the division rate and postpones 

 death. 



