GROWTH 257 



are HgCl2, CuCh, ZnCl2, AS2O3, H2Cr207, HCHO, 

 CeHsOH, lysol, atropin, saponin, malachite green, 

 methyl orange, methylene blue. With some toxic 

 compounds, however, no stimulation could be noticed 

 in any concentration; among these were FeCls, KMn04, 

 iodine, acetate of lead and of aluminum. 



Hofmann's data show further there markable fact 

 that the number of colonies from the same amount of 

 bacterial suspension is increased by certain doses of 

 poison. This can mean only that certain cells too weak 

 to reproduce on normal agar (see p. 271) can be stimulated 

 by a small dose of toxic substance sufficiently to produce 

 normal colonies. 



A general explanation for the stimulating action of 

 chemical poisons has been given on p. 137. The evidence 

 given here is quite sufficient to show that even through 

 a large number of generations, chemical stimulation 

 does not necessarily mean a final detriment to the cell. 



V. MECHANISM OF GROWTH 

 (a) MOLECULAR STRUCTURE OF THE CELL 



Growth, chemically speaking, is essentially a process 

 of dehydration and of reduction. Doubtless, breaking- 

 down processes such as hydrolysis and oxidation will 

 also take place, but the outstanding, dominant problem 

 is that of construction either by removal of water, or by 

 reduction, or by other means. 



While the preceding pages have shown how the growth 

 mechanism reacts upon certain environmental conditions 

 such as concentration of food, temperature, kind of food 

 and stimulants, the mechanism as such has not been 

 discussed. In this chapter, an effort is made to obtain a 

 conception of it. The difficulty of a clear understanding 



