108 IRRITABILITY 



essential data for the assumption of the existence of such pro- 

 cesses which regulate the transformation of reserve substances 

 as well as its extent. Pfeffer 1 has found in several fungi and 

 bacteria that there exists a compensation between the diastatic 

 breaking down of the carbohydrates stored as reserve material 

 and the quantity of dextrose introduced. He further found that 

 the more the reserve substance is split up into dextrose the less 

 of the latter is introduced from without and vice versa. De Bary 2 

 some time ago also observed in the bacillus amylobacter an analo- 

 gous relation between the enzymatic cellular digestion and the 

 quantity of dextrose introduced with the food. An equilibrium, 

 therefore, exists between the required amount of dextrose and 

 the extent of enzymic splitting up processes of the reserve mate- 

 rial. A great number of similar processes have been observed. 

 Even though the details of the whole preparatory assimilative 

 processes are beyond our knowledge we can still say with certainty 

 that, on the one hand, everywhere great quantities of organic 

 reserve substances are always present in the cell, and on the other, 

 that these substances are subjected to a transformation into suit- 

 able material for building-up processes, the extent of which is 

 controlled according to need, by the processes of self-regulation. 

 Entirely different is the question if the cell also possesses a 

 reserve store of oxygen. In this respect views have widely 

 differed, and even today no conformity of opinions has been 

 arrived at. The fact that many purely aerobic organisms and tis- 

 sues can exist under complete exclusion of oxygen for a longer 

 or shorter period, retaining their excitability and producing car- 

 bon dioxide, has for a long time led a great number of investi- 

 gators, such as Liebig, Matteucci, Engelmann, Pettenkofer and 

 Volt, Claude Bernard, Verworn, H. v. Baeyer and others, to the 

 supposition that a reserve store of oxygen must exist in the living 

 substance which maintains its excitability for a time. More 

 recent information, however, of the transition of the oxydative 

 to the anoxydative disintegration under a deficiency of oxygen, 



1 W. Pfeffer: "Ueber die regulatorische Bildung von Diastase." In der math. phys. 

 Klasse d. Konigl. Sachs Ges. d. Wiss. zu Leipzig 1896. 



2 De Bary: "Sur la fermentation de la cellulose." In Bull, de la Soc. bot. de 

 France 1879. 



