48 
bacteria with phenol, the molecules (MN) of phenol reacting with 
those of the bacterial constituent are in the proportion of 5.5 to 1. 
As regards the metallic salts the same law holds good for disinfee- 
tion by silver nitrate and the molecules (V) of silver nitrate reacting 
with those of bacterial constituents are in the proportion of 1:1. 
In the case of Mercurie chloride, however, the above relation between 
the concentration of disinfectant and the average velocity of disin- 
fection is maintained only if the former is expressed in terms of 
the corresponding concentration of mercuric ions. Under these cir- 
cumstances, MN has the value 4.9 for anthrax spores and 3.8 for 
paratyphosus. But the temperature coefficient of the disinfection by 
phenol is very high, though the reaction is approximately hepta- 
molecular. On the other hand, in the case of silver nitrate the 
reaction is approximately bimolecular and the temperature coefficient 
is small viz. 2 for a 10° rise. These results are contrary to our 
experience in ordinary chemical reactions, where the greater the 
order of a reaction the smaller is the coefficient of temperature. 
Kanitz (Temperature und Lebensvorgänge,, 1915), Snyper (Amer. 
Jour. of Physiol. 22, 1908, 309), Conen Sruart (Proc. K. Akad. 
Wetensch. Amsterdam, 1912, 20, 1270), Péirrer (Zeit. Allg. Physiol 
1914, 16, 617) and others have tried to represent the influence of 
temperature on physiological processes by the rule of van ’T Horr, 
but it is not very important whether the temperature coefficient has 
the value 2 or 3, the important point to establish is whether the 
formula of ArrueEntus (Zeit. Phys. Chem. 1889, 4, 226) or the formula 
of Harcourt and Esson (Phil. Trans series A Vol. 186, 817 (1895), 
Vol. 212, 187, (1912), which is applicable to ordinary chemical 
reactions, is also applicable to physiological processes. 
BrACKMAN (Annals of Botany 1905, 19, 281) has accepted the 
validity of the van ’t Horr rule and has found the value 2.1 between 
9° and 19°. He has assumed that this value of the temperature 
coefficient remains constant at higher temperatures; this assumption 
is contrary to our experience in ordinary chemical reactions, the 
temperature coefficient for a 10° rise becomes smaller as the temperature 
rises. This falling off of the temperature coefficient with increase of 
temperature is also expected from the Arruenius formula. Evidently 
the conclusions of BrACKMAN would have been more correct had he 
accepted the ARRHENIUS formula. 
Looking at the whole problem from a broad point of view it 
seems that temperature has two effects on vital processes: — (a) the 
increase of the velocity of the chemical reaction involved in the 
physiological changes, (b) the destruction of the living cells. 
