Apr. 15, 191S Disinfectiofi of Hides 67 



mann and Marmann (4) as the result of comparative experiments with 

 the Seymour-Jones and Schattenfroh methods. 



Sevcik's comparison (14) of the two methods is interesting, but is not 

 fair to the Schattenfroh method, as he admits, because of the use of 

 solutions based on the percentage of "hydrochloric acid" rather than on 

 the percentage of hydrochloric-acid gas. 



EXPERIMENTAL WORK ON GERMICIDAL EFFICIENCY OF 

 DISINFECTANTS 



The experimental work was undertaken primarily with a view to 

 determining the value of the Seymour-Jones method, and for that rea- 

 son this paper deals largely v/ith work done with that method, although 

 some attention was paid to others, especially the Schattenfroh method. 



In the absence of a supply of naturally infected hides it was necessary 

 to make the experiments upon pure cultures and artificially infected 

 pieces of hide. Although Sevcik (14) states that naturally infected 

 hides are better for test preparations than those artificially infected, it 

 does not seem that the difference is as great as he claims. Certainly his 

 results with naturally infected hides, where the disinfectant was not 

 neutralized, correspond very closely to results obtained b> Ponder (9, 10) 

 with artificially infected hides. 



EXPERIMENTAL PROCEDURE 



For preliminary work the Hill "rod" method (5) seemed best adapted; 

 so this was used, with some modifications. The method as modified is 

 as follows : Glass rods three-sixteenths of an inch in diameter and 8 inches 

 long are etched at one end, the etched portion being about i inch long. 

 Cotton is wrapped about the rods near the end not etched and the rods 

 thrust into test tubes so as to engage the cotton in the mouth of the 

 tube. The tubes containing the rods are sterilized by dry heat (150° C.) 

 for one hour or more. In making tests the rods are removed and the 

 etched portion dipped into a suspension made from a culture of the 

 organism employed and this allowed to dry on the rod. 



Rods so infected are transferred to test tubes containing the disin- 

 fectant to be tested and there exposed to its action for varying lengths 

 of time. After exposure the rods are washed with sterile water in order 

 to remove traces of the disinfectant and are then transferred to tubes 

 containing bouillon or agar, which are incubated for at least 48 hours at 

 37.5° C. The suspension used in infecting the rods is made from the 

 surface growth on an agar tube by rubbing up in several cubic centimeters 

 of sterile water enough of the growth to give a suspension of approxi- 

 mately the same density as a 24-hour bouillon culture of Bacillus typhosus. 

 For a non-spore-bearing organism the culture should be 24 hours old, 

 while for spore-bearing organisms cultures i to 2 weeks old are usually 

 the most suitable. 



