460 Profs. Percy Frankland and Marshall Ward. 



at even 35 or 36 C., in the minimum time i.e., thirty minutes or 

 so but the second doubling of the same filament will require a longer 

 time, and the third may occupy nearly twice as long, and so on, as is 

 well seen from the curves of November 5. 



Another way of putting it is the following the higher the tem- 

 perature (up to the limit) is above the optimum the sooner the total 

 growth of the organism is- completed, but as the rate of this growth 

 does not increase beyond that of the thirty minutes doubling period, 

 the total length of the filament produced is proportionately less than 

 would have been produced nearer the optimum, i.e., the total crop is 

 a smaller one. 



As I understand it, this action of temperature is on the life of the 

 organism, and not a mere exhaustion of the food-medium ; and I 

 suppose that in like manner the action of the blue rays of light is 

 similarly on the organism, and not merely on the food-medium. 



But it by no means follows that the food medium is totally exempt 

 from oxidation under the action of both temperature and light ; and 

 in the case of such extremely oxidisable media as peptone-meat- 

 broth, and similar compounds, the constitution of which approaches as 

 near to the bodies concerned in metabolism as any media physiologists 

 have been able to prepare, we must not be surprised to find that they 

 undergo oxidation outside, as well as inside the living cells, especially 

 when enzymes are present, under the action of light and high tem- 

 peratures. 



Many of the experiments point to this conclusion, and it is par- 

 ticularly to be noticed that the food-medium seems to become more 

 and more subject to such oxidations promoted by high temperatures 

 or by light when the action of the peptonising enzymes, which they 

 excrete, is in full swing, as if the whole system cell plus its pepto- 

 nised medium of the hanging-drop were respiring, so to speak. 



It will, I think, be worth while to institute a careful series of 

 experiments specially directed to secure information on this head ; 

 for it opens up a very large and important question. 



Elfving's researches* have, it seems to me, already rendered it 

 extremely probable that, in the case of the fungi he examined, the 

 action of the light is to destroy, by promoting oxidation, the con- 

 structed metabolites at the 'moment they are about to be assimilated. It 

 looks, in fact, as if the materials to be built up in the protoplasmic 

 structure are in a dangerously unstable explosive, if you like con- 

 dition, and no doubt it is at this period that the damage is done, 

 probably in the machinery of the cell itself, though it is not impossible 

 that it occurs outside the actual machinery, in vacuoles, for instance. 



Now peptone- broth, when saturated with enzymes of the kind referred 

 to, is doubtless an extremely unstable medium, and probably in a 

 * Elt'ving, " Studien iiber die Einwirkung deo Lichtes auf die Pilze," 1890. 



