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THE AMEBIC AN NATURALIST [Vol. XL VII 



ment is insufficient. For these reasons an inhalation 

 method of treatment has been resorted to which, as far as 

 experience goes, has no serious disadvantages and does 

 not complicate the conditions of the experiment. 



A fume tank of copper is made of sufficient size to 

 supply breathing space for 4 or 5 guinea-pigs at one time. 

 The tank is arranged with four outlets, so that definite 

 amounts of the fumes may be passed through in a given 

 time and the ventilation controlled. In this way each 

 animal could be given about the same amount of the sub- 

 stances. The individuals, however, differ so in their 

 resistance to the treatment that it has been found better 

 to treat all to about the same degree of intoxication. This 

 physiological index is more reliable as each animal is 

 thus affected in a similar fashion each day. For this 

 purpose they are placed in the fume tank on a wire 

 screen, and absorbent cotton soaked with alcohol is placed 

 beneath the screen, and the animals inhale the fumes. 

 The tank was described and illustrated in a previous 

 article. 



Ether is given in a similar manner, except that the 

 animals are much more readily overcome and must be 

 carefully watched while inhaling even the most dilute 

 doses. 



In order to avoid handling the females during late 

 pregnancy, a special treating cage is devised. An ordi- 

 nary box-run with a covered nest in which the animal 

 lives is connected by a drop-door with a metal-lined tank, 

 having a similar screen arrangement to that of the gen- 

 eral treatment tank. The pregnant animal may be 

 driven daily into the tank and thus treated with alcohol 

 fumes throughout her pregnancy without being handled 

 in any way that might disturb the developing fetus. 



Direct Effects of the Treatment on the Animals 

 Many of the animals have now been treated almost to 

 the point of intoxication for six days per week for nearly 

 three years. They are affected by the alcohol fumes in 



