THE ANIMAL A MACHINE 175 



seemed to be the result of a vital force. Nowadays there 

 is no necessity for such an assumption, but vital force 

 is still thought to play a part in unexplained phenomena, 

 such as the contraction of a muscle. Does it not seem 

 more reasonable to admit our ignorance and to make seri- 

 ous attempts to develop experimentation to a higher level? 



The very fact that the experiments described can be 

 performed with any kind of oil indicates that they must be 

 deficient in some respect. The liquid matter of an Amoeba 

 is certainly different from any simple oil. One point of 

 distinction is that in the Amoeba — as in all living things 

 chemical changes are continually occurring. In the course 

 of these changes substances are being formed which diminish 

 the surface tension and consequently lead to the protrusion 

 of pseudopodia. Nothing of the kind occurs in a simple 

 oil-drop; "pseudopodia" will protrude from it only if a 

 substance such as alcohol is added to lower surface tension. 



But it should also be possible to find an oil in which cer- 

 tain chemical changes occur. A droplet of such oil might 

 produce within itself substances which diminish the surface 

 tension thus imitating more satisfactorily the conditions 

 prevailing in Amoeba. Can such an oil be obtained? 



This task has been solved through work undertaken at 

 the suggestion of Dr. G. W. Crile, surgeon and scientist of 

 Cleveland, Ohio, who conceived the idea of studying the 

 actions of materials extracted from the brain of freshly- 

 killed animals. With the cooperation of an excellent ex- 

 perimentalist, Dr. M. Telkes, who worked in Crile's research 

 laboratory in the Cleveland Clinic, this idea was carried out 

 in 1931. Dr. Telkes extracted the oil from the brain of 

 freshly-killed rabbits so skillfully as to preserve at least 

 some of the essential properties of the material, particularly 

 its enzymes (chemical activators). 



Just as olive-oil is pressed from ripe olives, or cotton-seed 

 oil from the seeds contained in cotton, so it is possible to 



