PROTOPLASM 19 



the presence of sugar appears to be actually injurious to the growth of the 

 organism. Hydrogen gas can also be used as a source of energy. When hydrogen, 

 oxygen, and carbon dioxide are present together, it is found that the oxygen is used 

 up to oxidise hydrogen, and the energy so obtained enables the carbon dioxide to be 

 used as a source of carbon : the three gases disappear simultaneously. Another 

 interesting fact is that sulphur organisms also require a supply of carbon dioxide 

 in the form of carbonate. 



Evidence will be given in Chapter XX. and elsewhere against the supposed 

 existence of intramolecular oxygen. In fact, a view akin to that of Hofmeister 

 (1901) is rapidly gaining ground. Hofmeister looks upon the cell rather as a 

 laboratory, in which various operations are going on at the same time, being kept 

 apart by membranes or partitions of some kind. Hopkins (1912, p. 220) advocates 

 the existence of " interplasmic " reactions, in which substances formed by proto- 

 plasm are responsible for chemical changes in the cell. These reactions, then, take 

 place in interspaces between the protoplasmic molecules, or rather molecular 

 aggregates, themselves. Digestion in food vacuoles of Amoeba may serve as an 

 illustration of the process on a relatively large scale. Other reactions may occur 

 in similar spaces, too small to be visible under the microscope. It seems that 

 living matter is a complex of association processes of various types, in which 

 physical forces play a large part, such as the surface condensation known as 

 "adsorption" (Chapter III.), and also electrical charges. These forces control and 

 regulate the course of the chemical reactions (Hopkins, 1912, p. 218). In any 

 case it is evident that protoplasm, as it presents itself in such an organism as 

 Amoeba, is a system of many components or phases, solid and liquid, minutely 

 subdivided and intimately mixed (see Gaidukov, 1910, pp. 61, 62, 74). In a 

 certain sense, therefore, it may be said to have a structure, and the fact is of 

 interest in connection with such chemical reactions as cease when the cell is 

 ground up in a mortar. The cessation of the oxidation of lactic acid in muscle 

 when chopped up (Fletcher and Hopkins, 1907, p. 284, and Harden and Maclean, 

 1911, p. 45) may be referred to. The effect produced by change of distribution of 

 phases, as in Fig. 15, must also be borne in mind. Vernon (1912, pp. 210, 211) 

 has been led, by his work on the effect of anaesthetics on oxidation in cells, to 

 suggest the separation of cell constituents by membranes of a lipoid nature, a view 

 similar to that of Hofmeister. Buchner (1903, p. 92) noticed that yeast cells 

 containing glycogen showed no " auto-fermentation " as long as they were alive, 

 but, when killed by acetone, this took place. Obviously, during life, the .access of 

 zymase and other enzymes to the glycogen is not permitted to take place. 



A discussion of phase relations in protoplasm with respect to equilibrium and energy will 

 be found in the essay by Zwaardemaker (1906, pp. 137-154). 



As already pointed out above, protoplasm usually presents the characters 

 of a liquid, but when dead it appears to take on a rigid structure, like melted 

 jelly when it "sets," or egg-white when boiled. In this state it is no longer 

 a liquid, and the Brownian movement of particles contained in it ceases, as 

 they are held in a fixed structure. 



An observation made by Gaidukov (1910, p. 58) suggests that such a change may take place 

 temporarily during life ; if so, this may be a means of localising chemical changes in particular 

 parts of the cell. When protoplasm presents a free surface to watery fluids it is found to 

 exhibit a continuous movement. In vegetable cells these movements are of a circulating or 

 streaming nature. Now Gaidukov noticed, when observing the phenomenon in Vcdlisntna, 

 that the streaming movement occasionally ceased and only a few of the particles showed 

 Brownian movement. Presently, the Brownian movement began to reappear, and, as it 

 increased, the streaming recommenced. This looks very much like a reversible change from 

 "sol" to "gel." 



The " Biogen " theory is an example of the efforts of a certain school of 

 physiologists to explain by purely chemical laws, such as mass action, facts 

 which admit of simpler explanation, if physical phenomena are also taken into 

 account. Forced and elaborate assumptions are sometimes necessary if chemical 

 laws only are allowed. If a physical explanation' is forthcoming, it appears 

 to me that it is more scientific to adopt it. It may be said indeed that it is 



