30 



DE. BASTIAN ON THE 



by either of these investigators. The trials they have made 

 most closely resemble those experiments of mine which illus- 

 trate the effects of adding liquor .potassae in excess ; and the 

 results they have obtained tend to confirm mine, and illustrate 

 the restrictive influence of even a slight excess of this agent. 



I now turn to the subject of Dr. Eoberts's criticism of my 

 method, because in pointing out the untenability of his positions 

 T shall be able to throw some light upon the subject generally. 



Two objections have been raised by him to the mode in which I 

 conducted my experiments, seemingly on the ground that in the 

 five experiments of this order which he had previously made, two 

 procedures were adopted which I did not imitate. Dr. Eoberts 

 thinks that I ought (1) to have superheated the liquor-potassae 

 tubes ; and he thinks (2) that I ought to have allowed an interval 

 of some days to elapse before breaking them and permitting the 

 potash to mix with the boiled urine. Both these objections are 

 indorsed by Professor Tyndall ; and, as we have seen, an objection 

 very similar to the first of them had previously been urged by 

 M. Pasteur ; they require, therefore, to be critically examined*. 



(1) Is it necessary^ or does any difference result from superJieat- 

 heating the potasli-tubesl — To the first part of this question I 

 had, previously to the date of my first communication on this 

 subject, given an answer in the negative, and that for the follow- 

 ing reasons : — 



(a) Quite early in this investigation I made comparative experi- 

 ments to test whether any or what influence over the result would 

 be produced by prolonging the period for which the closed liquor- 

 potassse tubes were heated ; so that Dr. Eoberts is in error in 

 supposing that they had been raised only for "an inconsiderable 

 period to the heat of boiling water." In the majority of the ex- 

 periments they were heated to this extent for over twenty 

 minutes ; and in several of them they were boiled for one and 

 two hours. It was only when I found that this prolongation 

 of the boiling of the liquor-potassse tubes did not in the least 

 affect the result that I contented myself with the shorter period 

 of twenty minutes. 



^ M. Pasteur urged the superheating of the potash-tubes on the ground, as 

 above pointed out, that a temperature of 110° 0. was needed to ensure the death 

 of germs even in a strong solution of caustic potash. Dr. Roberts does not ven- 

 ture so far as this. He considers the high temperature needful in order to 

 ensure sterilization of the air within the liquor-potassas tubes. 



