70 



THE AMERICAN NATURALIST 



[Vol. L 



lation method of treatment was resorted to early in the 

 study, and, as far as experience goes, it has no serious 

 disadvantages and does not complicate the conditions of 

 the experiment. 



This method may be merely described in brief for the 

 convenience of the reader, since it has been fully recorded 

 with illustrations of the fume tanks in previous publica- 

 tions. A fume tank of copper is made of sufficient size 

 to supply breathing space for four or five guinea pigs at 

 one time. The tank has four outlets, so that a definite 

 amount of fumes may be passed through in a given time 

 and the ventilation controlled. In this way each animal 

 could be given a definite measured dose. The individ- 

 uals, however, differ so much in their resistance to the 

 treatment that it has been found better to treat all to 

 about the same degree of intoxication. Such a physio- 

 logical index is more reliable, since every animal may be 

 affected to the same degree each day. For this purpose 

 the animals are placed in the fume tank on a wire screen, 

 and absorbent cotton soaked with alcohol is placed be- 

 neath the screen, so that they inhale the alcohol fumes 

 arising from the cotton to saturate the atmosphere of the 

 tank. 



Ether was given in a similar manner. The animals 

 are much more readily overcome by these fumes and 

 must be carefully watched while inhaling even the most 



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, etc., to that of the general 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 



