338 



RUEDIGER. 



Table IV.- 



-Typhoid agglutinating nerum unfiltered A, and filtered V, N and W 

 tested for its agglutinating value. 



Dilution. 



I'ortioii. 



Time. 



1 

 1 



A. 



V. 



N. 



W. 



1-100 - 



+ 

 + 



+ 



+ 



-1' 

 -1- 

 + 



-1- 



+ 

 + 

 + 



+ 



+ 

 + 

 + 

 -1- 

 + 

 + 

 ■f 



Hours. 1 



+ 9 i 



1-200- 



-J- ; 9 



1-400 



+ ! « 



1-800 



+ 

 + 



+ 



9 

 9 

 9 

 9 

 9 

 9 

 9 



1-1, 000 



1-1,400-.—- 



1-1,800 



1-2,200 



1-2,600 



1-3, 000 



1-3,200.- ■-. 



- 9 



— 9 



l-(i,400 



A glance at Table IV shows the agglutinating value of the filtered 

 portions V, !N" and W to be practically identical with that of the un- 

 filtered portion A. 



EXPERIMENT V. 



The influence of high pressure on the permeability of Berhefeld filters 

 to small yet microscopically visible bacteria. 



It has been Imown that bacteria which are not ultramicroscopic may 

 and will pass through the pores of Berkefeld filters. Wherry *, in the 

 year 1902, showed that the bacillus of guinea pig pneumonia frequently 

 passes through the Berkefeld filters under ordinary conditions of filtra- 

 tion. 



In this laboratory, the Berkefeld filter marked W is used almost 

 exclusively for the final filtration of anticattle plague serum. Filtration 

 was formerly carried on with the Chambeiiand filter stand under a pres- 

 sure of one and one-half to two atmospheres ; bacterial contamination of 

 the filtrate was rare, but the filtration frequently was slow and tedious. 

 In order to facilitate the filtration the air pressure in the institution, 

 which is kept fairly constant by an automatic electric regulating device, 

 was increased to four atmospheres. Bacterial contamination of the filtrate 

 soon became common and the contaminating organism usually was a 

 small bacillus. This at once led me to study the influence of various 

 pressure on the permeability of the filters to these bacilli. 



Method of investigation. — Nine new Berkefeld filters, three marked V 

 and designated here as V,, V„, and V„„ three marked N, designated 

 Ni, Nii, and N,„, and three marked W designated Wj, W,i and W„i 



*Journ. Med. Research (1902) 8, 322. 



