126 THE AMERICAN MONTHLY [June, 



of carbon compounds, proteid which is nitrogenous, carbohydrate, or 

 starchy matter and fat. The particular kind of proteid, starch, or fat 

 is not constant, but varies with the location of the protoplasm. It will 

 be well for us to note here and keep in mind the fact that these organic 

 compounds constituting protoplasm are of high potential energy. They 

 have been made the reservoirs of forces (derived in the first instance 

 from the sun) . They are hence unstable, and under suitable conditions, 

 viz., heat and the presence of free oxygen, they will " break down" 

 into simple mineral compounds of the same elements as compose them, 

 at the same time setting free for work the force which had iDeen latent 

 before the oxidation. 



4. Powers of Protoplasm. — The marvel about protoplasm is that it 

 can do such wonderful things. It can weave, and spin, and brew. 

 All that living things can do are done through it so far as we have 

 learned. The various powers of protoplasm are best considered sepa- 

 rately and they may be considered under three heads : First, the power 

 of regulating chemical changes, called in scientific diction metabolism ; 

 second, the power of changing the position of its components, and 

 hence its shape, called the power of inovement ; and third, the power 

 of responding to any impression from without, together with the power 

 to retain the efl:ect of the impression or transmit it, possibly all phases 

 of the same power, called ii-7'itahility. Each of these we shall now 

 consider. 



5. Metabolism. — Living protoplasm can regulate chemical action. 

 It can check it and thus prevent oxidation of its unstable compounds, a 

 tendency at once followed by dead protoplasm unless prevented by 

 some preservative precaution, or it can allow oxidation to go on in cer- 

 tain degrees. It can inaugurate chemical reactions by presiding, one 

 might say, over the march of atoms to and from ranges of attraction 

 which would result in the production of certain compounds. One of 

 the most easily noticed cases of this power of protoplasm is exhibited 

 by the germinating seed, as for instance that of the bean. This seed, if 

 placed on a moist sponge and kept warm, will soon soften, swell, and 

 split open. A young sprout plainly seen within will elongate and soon 

 become a pair of genuine leaves, with ribs and leafy shape and texture, 

 but white. Later, however, the leaves become green. This green 

 matter, chlorophyll., is a peculiar chemical of well-known composition. 

 Its color ought to help us to find it in the ungerminated seed if it has been 

 stored away there, bnt we cannot find it there. It must, then, have 

 been made "by the protoplasm of the bean. Now, though chlorophyll 

 does not exist in the plant, other compounds do exist there which can 

 be made over into chlorophyll by taking out an atom here and there 

 and re-arranging the compound, and this the protoplasm can do. This 

 is metabolism. There are two sorts of metabolism ; one in which the 

 protoplasm alters compounds from more complex to less complex ones. 

 This kind predominates in animal protoplasm and is called destructive 

 metabolism or katabolism. Another, in which the protoplasm builds 

 more and more complex compounds out of simple ones, is called con- 

 structive metabolism or anabolism, and is characteristic in a broad sense 

 of vegetal protoplasm. 



6. Movement. — It is obvious upon reflection that the power of 

 metabolism, or we may say self-control over chemical reaction, is not of 



