178 life's beginning on the earth 



a more alkaline solution they may be very broad. (Fig. 

 72.) It will be remembered that the simple oil-drops were 

 also capable of sending out either thin pseudopodia or quite 

 broad ones (Fig. 66). 



The droplets of fresh brain -oil are obviously more in- 

 volved than those of an ordinary oil like olive oil. Those 

 with slender protrusions have a special structure in then- 

 center which gives them a strange appearance, as an in- 

 spection of Figure 71 shows. At first glance this center 

 structure looks like the nucleus of a living cell. In reality 

 it is a small drop of water enclosed in the oil droplet. Into 

 this internal droplet of water, the same kind of slender 

 pseudopodia will grow as grow from the periphery of the 

 drop. This double development, from the periphery as 

 well as to the inside, gives the whole structure its peculiar 

 appearance, remotely reminding one of a living cell. But 

 it would be absurd to maintain that an oil-droplet from 

 fresh material is alive. A true life-like growth signifies an 

 increase of the mass, and this never occurs in the oil-drop. 

 On the contrary, it decreases in size after many hairlike 

 pseudopodia have protruded from it. 



The outstanding feature of living things is that chemical 

 changes occur in them. Is it possible to demonstrate chem- 

 ical changes in these oil-drops? 



The chemical changes occurring most commonly in the 

 animal body are those of respiration. These include the 

 taking in of the oxygen of the air which is used to burn a 

 part of the body material. Modern scientists have devel- 

 oped methods which make it possible to measure the degree 

 of this respiration even with very small fragments of ex- 

 cised tissues, or with only a few living bacteria, in spite of 

 their diminutive size. Dr. Telkes made the important 

 discovery that droplets of brain-fat also exhibit respiration, 

 thus demonstrating that chemical reactions occur in this 

 fat. In the course of these reactions, substances are formed 



