( 600 ) 
at that temperature, and on the ground of the literature there- 
about he thinks this must be considered as a common phenomenon. 
That at temperatures above 30° with continued fore-heating an 
increase of the praesentation time is obtained, should now, according 
to Ruregrs, be ascribed to the fact that the favourable action of the 
continued fore-heating is quite annulled by the noxious influence 
arising at the same time. Such a noxious action might, according to 
Rureers, in his experiments already be active at 30°C., but there 
the favouring by continued fore-heating would be greater than the 
injury. Rureers thinks this must be concluded from the fact that the 
curve, found by him by extrapolation for a time O of fore-heating, 
at 30’, indicates a lower value of the praesentation time than that 
practically found after 1 hour’s fore-heating. 
If now it is right that also at higher temperature than 30° a 
favouring influence by continuation of the fore-heating may be ad- 
mitted, the values found for the praesentation times after 1 hour, 
2 hours, ete. of fore-heating, would, without that favourable action, 
be higher than they are now. 
After Rureers it is on this account not allowed to draw con- 
clusions after different times of fore-heating about the praesentation 
time or the velocity of a physiological reaction (indifferently whether 
this is done by calculation as in our method or by extrapolation as 
in that folloveed by Brackman and others), if no account is kept 
with the favourable influence of continued fore-heating. He thinks that 
if this is done, BLACKMAN’s theory for the explanation of the tempe- 
rature-optimum proves to be right and that for the relation between 
temperature and praesentation time, resp. the velocity of the reaction 
at a fore-heating time of 0, a curve without minimum resp. optimum 
will be found. 
It may be remarked here at once that Rurarrs has not confirmed 
by observations this modified theory of BLACKMAN. For this a special 
study of the noxious influence by continued fore-heating would 
have been required and sufficient; such a study, however, has not 
been made and hence, the testing of his theory with his own results 
is impossible. 
Mr. Rvureers has thus only pointed to the “possibility” that this 
modified theory of BrACKMAN might give an explanation of the 
phenomena. 
We now wish to prove that this modified theory is not confirmed 
by our observations, without the support of new accessory hypotheses. 
To this end we state that, according to Rutgers, the considerable 
deviations from the rule of van’r Horr, too, may be explained by 
