THE ANIMAL A MACHINE 181 



finding we may conclude that, through nervous exhaustion, 

 the very substance of the brain is changed. 



Another striking feature of the oil-drops freshly prepared 

 from brain is that they can be poisoned. Every one is 

 familiar with the action of poisons upon human health and 

 life. Science has made a special study of those poisons that 

 do not act upon all organs at the same rate. They strike 

 only certain portions of the body, but may strike so hard 

 that this part is completely paralyzed. Usually some vital 

 portion of the brain is thrown out of gear. The conse- 

 quence is extremely grave; death quickly follows in most 

 cases. To this class belong strychnine, morphine, and 

 many others. 



Many of these poisons act also upon the Amoeba. The 

 poisoning is recognized by the disappearance of the pseu- 

 dopodia while the animal becomes stationary and rounds 

 up. After a while the cell falls into shreds which gradually 

 dissolve. The same poisons will also "kill" the oil-drop. 

 The drop no longer grows hairlike processes, nor maintains 

 the internal structure described, but rounds up to a dark 

 massive drop, like the oil obtained from the brain of ex- 

 hausted animals. It is of great importance that we can study 

 in this manner the action of poisons on oil-drops of brain-fat. 

 Life in the usual sense of the word cannot possibly reside 

 in an oil-drop; only certain life-like properties have been 

 retained by it. These properties are destroyed by poison 

 and the drop rounds up. Here is a specific action which is 

 not exhibited by other artificial structures such as the in- 

 organic growths of Leduc (Figs. 39-52), which are quite 

 different from living things as far as their chemical make-up 

 is concerned; nor is this specification exhibited in oil-drops 

 of ordinary oil. 



The nature of the specific action by which the poison acts 

 on the brain-fat-drop has been investigated by Dr. Telkes. 

 The action comes about through an inhibition of respiration 

 of the oil drop (described above, page 178) as has been 



