38 



LIFE: ITS BEGINNINGS AND NATURE 



l^» 



Fig. 2-16. A living amoeba, when viewed under the 

 light microscope, gives us some clue as to the nature 

 of protoplasm. Note the clear protoplasm that con- 

 stitutes the pseudopods and the more or less opaque 

 region that makes up the bulk of the cell. Tiny par- 

 ticulate matter floats about in the body of the cell, 

 conveying to it a gray color. 



material from within the cell. The most 

 striking fact that one observes is that the 

 entire mass of protoplasm is moving in 

 what appears to be a more or less hap- 

 hazard manner, even though the general 

 flow is in the direction the organism is go- 

 ing. Another important observation is that 

 there appears to be many different kinds of 

 particles suspended in this semi-fluid, semi- 

 solid material. Some of the particles seem 

 quite uniform in shape, whereas others are 

 variable. Among them is the large flattened 

 nucleus, several food vacuoles, and a clear 

 pulsating vacuole, none of which will con- 

 cern us now since they will be discussed 

 later when we examine this little animal 

 more thoroughly. Our concern now is with 

 the material in which all of these are sus- 

 pended, that is, the protoplasm. 



Our observations so far tell us very little 

 about the nature of protoplasm, but we can 

 try a few experiments on it. For example, 



we can drop a little alcohol or mercuric 

 chloride on it to see what happens. All 

 activity suddenly stops, and the entire cell 

 becomes rigid, much like the white of an 

 egg when cooked. It coagulates and be- 

 comes slightly opaque. Nothing we can do 

 will revive it, it has died, and in so far as 

 we know now this is an irreversible reac- 

 tion. It could then be given to the chemist 

 who is able to give us a list of the elements 

 and compounds of which it is composed. 

 After this and many other experiments, we 

 would still know very little about how the 

 amoeba moved, how it reproduced, or how 

 it carried on its metabolism. We need still 

 more refined techniques if more is to be 

 learned. Lacking these, we can only specu- 

 late from this point on, in order to obtain 

 a little better picture of what happens in 

 this beautifully complex protoplasm. 



Let us suppose that we could magnify 

 the protoplasm of an amoeba until we could 

 observe its molecular structure. This is be- 

 yond the power of the electron microscope, 

 which can magnify 100,000 times. The mi- 

 croscope we have in mind would also need 

 to be designed to view living material, 

 something the electron microscope cannot 

 do. The most obvious characteristic, as we 

 peer at this blob of protoplasm, would be 

 the violent activity of molecules of all 

 shapes and sizes. The most numerous would 

 be the water molecules, which, because of 

 their small size, would move faster than 

 most molecules. Huge, slow moving mole- 

 cules would be bound together, forming 

 a continuous network of material that re- 

 mained in one place most of the time, as 

 an outer boundary of the cell marking it 

 off from the outside world. This would be 

 the plasma membrane, through which the 

 water m.olecules pass freely in both direc- 

 tions. Many other molecules pass through 

 also, but some are stopped because of their 

 large size, whereas others are stopped be- 

 cause they possess electrical properties that 

 prevent them from getting past the electri- 

 cal barrier on the membrane. Oxygen mole- 



