Apr. IS, 191 5 Disinfection of Hides 75 



Ten pieces of hide were exposed for 24 hours to 25 c. c. (for each piece) 

 of mercuric chlorid, i to 4,000, plus i per cent of formic acid, and then 

 soaked 24 hours in a saturated common-salt solution. The clots were then 

 scraped off and inoculated into guinea pigs. In one instance two clots 

 were inoculated into one animal ; in all other cases only one clot was used 

 (Table VI, experiment 11). 



Another experiment (Table VI, experiment 12) was made in which 

 six guinea pigs were inoculated with one clot each from pieces of hide 

 disinfected with mercuric chlorid, i to 4,000, plus i per cent of formic 

 acid; two guinea pigs were inoculated with two clots each from pieces 

 similarly disinfected; and one guinea pig was inoculated with five clots 

 from pieces of hide disinfected with mercuric chlorid, i to 2,500, plus i 

 per cent of formic acid. As in the preceding experiments, each piece of 

 hide was exposed for 24 hours to 25 c. c. of disinfectant and soaked in 25 

 c. c. of saturated common-salt solution for 24 hours, after which the 

 clots were scraped off and inoculated under the skin of the guinea pigs. 



The apparent discrepancy between experiments 11 and 12 in con- 

 nection with results obtained by inoculation into guinea pigs of clots 

 from two pieces of hide disinfected with mercuric chlorid, i to 4,000, 

 plus I per cent of formic acid, may be explained on the ground that the 

 pieces used in the second experiment had been kept longer than those 

 used in the first and had consequently lost virulence by continued drying. 

 Even in experiment 11 it will be seen that the disinfectant exercised a 

 marked influence on the virulence of the spores, since the guinea pig 

 remained alive until five days after inoculation. 



The results of these experiments are confirmed by the results of a fur- 

 ther experiment (Table VI, experiment 13) performed later with test 

 preparations of a different lot. This later lot was prepared in exactly 

 the same way as the earlier ones; but the culture used for infecting the 

 pieces of hide was obtained from a guinea pig dying a little more than 48 

 hours after inoculation, while the culture used for the pieces first pre- 

 pared was obtained from a guinea pig dying within 36 hours after inocula- 

 tion. The difference in the vitality of the spores is clearly seen in the 

 length of time necessary to kill the guinea pigs inoculated from the check 

 pieces. As will be seen by reference to Table VI, this time was about 

 48 hours for the first lot, while for the second it was from 4 to 5 days. 



In order to ascertain the effect of mercuric chlorid and formic acid 

 upon hides from the standpoint of the tanner, pieces of hide about 4 

 by 5 inches in size and weighing about 50 gm. each were disinfected by 

 the Seymour-Jones method, using mercuric-chlorid dilutions of i to 

 4,000 and I to 2,500 plus i per cent of formic acid. The proportion of 

 disinfectant used was 10 times the weight of the hide. These were ex- 

 amined and tanned in the Ivcather and Paper Laboratory of the Bureau of 

 Chemistry. Immediately after dehairing, these pieces of hide were ob- 

 served to be very much blackened, but after the full process of tanning 



