68 



Journal of Agricultural Research 



Vol. IV, No. I 



In making tests with disinfectants containing mercury it is advisable to 

 dip the rods into a saturated solution of hydrogen sulphid or an aqueous 

 solution of some sulphid before placing them in subculture tubes. In 

 this connection it should be mentioned that media of acid reaction have 

 been found to exert an inhibitory action upon the growth of Bacillus 

 anthracis after exposure to disinfectants. For that reason the media 

 employed in these experiments have been neutral or slightly alkaUne. 



A considerable number of tests by the rod method were made with 

 organic matter added to the disinfectant. This was done by removing 

 a certain portion of the total volume of disinfectant and substituting a 

 like amount of defibrinated blood. 



Inasmuch as the use of a solution of sodium chlorid did not seem essen- 

 tial in experiments upon "naked" anthrax spores, since this salt is said 

 by Seymour-Jones to be used in his method to reduce the swelling of the 

 hides caused by formic acid, a common salt solution was not used in the 

 "rod" method experiments. 



MERCURIC CHLORID AND FORMIC ACID 



I. EXPERIMENTS BY ROD METHOD, USING BUREAU OF ANIM.^L INDUSTRY STRAIN OF 



BACILLUS ANTHRACIS 



These experiments were designed to show the germicidal efficiency of 

 mercuric chlorid (HgClj) with and without formic acid (CHjOo) and 

 with and without the addition of defibrinatcd blood. 



In experiment i (Table I) the rods were infected by using an agar 

 culture 2 weeks old for making the spore suspension. Microscopical 

 examination of the suspension showed that plenty of spores were present. 

 Each rod was exposed to 5 c. c. of disinfectant for 24 hours and was then 

 washed in 20 c. c. of hydrogen-sulphid solution or sterile distilled water. 



The rods were then transferred to subculture tubes of exactly neutral 

 broth and incubated at 37.5° C. for three days. 



Table I. — Germicidal efficiency of mercuric chlorid, -with and without formic acid, and 

 of plienol by the rod method, without addition of organic tnatter<i 



EXPERIMENT I 



« Rods I, 2, and 3 washed with hydrogen-sulphid solution, and Nos. 4, s, 6, 7, and 8 with sterile water. 

 6 Not exposed. 



