THE ANIMAL A MACHINE 



Ktt 



The diagrams below indicate the type of movement. The 

 writer is much indebted to Dr. A. L. Herrera of Mexico who 

 very kindly sent him these pictures. The water in which 



Fig. 63 b. A Diagram Depicting the Movement of Oil-Drops 



Herrera was so impressed with the life-like movements of these oil- 

 drops and particularly the mutual suction which they exert upon each other 

 that he has given them a name reminiscent of the animal kingdom, col- 

 poids. (One-half natural size.) 



the drops move contains soda which is the necessary addi- 

 tion tending to interact with the oil chemically. 



Dr. H. S. Jennings, Professor of Zoology at Johns Hop- 

 kins University of Baltimore, has studied moving oil-drops 

 by means of a similar technique in which he uses olive oil 

 floating in glycerin; he adds alcohol as the substance which 



