( 847 ) 
when my own countrymen were concerned — also for instance when 
Mr. NieuweNnuis began to work with my method. Moreover I have 
published the method of making the needles, and have pointed out 
that any one can easily make the simple mechanism required *). 
Meanwhile I emphasise, that this has nothing to do with the 
modus operandi of the method. One can hardly for instance call the 
modus operandi of telephoning complicated, because the manufacture 
of the telephone mechanism is difficult. 
So much as regards the objections to my method, of which 1 
appreciate the last one — the difficulty of making the glass needles 
and the fact that they could not be obtained commercially; I am 
therefore all the more glad that this objection has been removed. 
I now wish to discuss the alterations introduced by Ninuwenauts 
in my method. 
Fearing the above mentioned imaginary danger in sterilising the 
isolation needles, NievweNHuis has preferred to make for each isola- 
tion a new needle which terminates in a globule instead of an 
eye and which must be fastened into the needle-holder by means of 
plaster of Paris. It seems unnecessary to show that this is much 
more cumbrous than working continually with the same needle, 
which, when necessary, is readily sterilized in the way described. 
One can work for years with a single needle; it is elastic and does 
not break unless it is knocked roughly or dropped. 
Niruwennuis has the needle fixed to a support stand, which stands 
separately next to the microscope, while in my apparatus the 
support and microscope stand on the same plate, so that a displace- 
ment of the support with respect to the microscope, for instance 
through a knock, is rendered impossible. In the support used by 
Niruwenunuis, the needle can be moved in 8 directions, which is 
quite superfluous if a mechanical stage is used, as I have done from 
the beginning. Meanwhile NiruweNnuis (p. 533) eventually came to 
the same conclusion. He further places the coverslip, in which the 
cell is to be isolated, under the microscope in a kind of chamber, 
which is quite open on one side in order to admit the isolation 
needle. In my apparatus the needle enters through a slit, which is 
closed with liquid paraffin. By this means a closed moist chamber is 
formed, which has the great advantage, that if a drop is placed on 
its floor, even the smallest isolated droplet does not evaporate, so 
that observations can be made on isolated cells for a whole day, 
1) Zeitschr. fiir wiss. Mikr. Technik Bnd. 24, 1907, p. 258. Burry — in his 
“Tuscheverfahren’” wrongly assumes that the price of this simple mechanism is 
100 Mk, which is the price of the apparatus for isolation. 
