36 BACTERIOLOGY. 



with water, and its efficacy tested by making inoculations from the 

 cultures in fresh media. The results were entirely in favour of 

 carbolic acid. Staphylococcus pyogenes aureus and Streptococcus 

 pyogenes were not destroyed, even when corrosive sublimate solution 

 of 1 in 1000 was allowed to act for an hour. In the case of the 

 cultures of streptococcus of erysipelas the results were different. 

 A solution of 1 in 10,000 had no effect, but 1 in 4,000, acting for 

 one minute, destroyed the culture. With carbolic acid the results 

 were very striking. Cultures were exposed to solutions of 1 in 20, 

 1 in 30, 1 in 40, 1 in 50, for one minute, five minutes, fifteen 

 minutes. The attempts to make subcultures in every case failed. 

 Carbolic acid 1 in 40, acting for only one minute, was sufficient to 

 destroy Streptococcus pyogenes and Streptococcus erysipelatis and 

 Staphylococcus pyogenes aureus. Further experiments were made 

 with tubercular sputum, the test being subsequent inoculation of 

 guinea-pigs. Corrosive sublimate solution as strong as 1 in 500 had 

 no effect, but 1 in 20 carbolic acid, shaken up with the sputum for 

 one minute, completely neutralised it. 



Koch's statements with reference to the germicidal power of 

 corrosive sublimate in extremely weak solutions had led Lister to 

 substitute it for carbolic acid as a detergent in surgery. The author's 

 experiments, which were undertaken in 1892, encouraged Lister to 

 revert to the use of carbolic acid, w-hich, indeed, had always proved 

 efiicacious in surgical practice. Lister pointed out that carbolic acid 

 has also the great advantage of combining eagerly with fats and 

 epidermis, so that the seat of operation can be effectually cleansed. 



These experiments also point to the conclusion that carbolic acid 

 should be used in hospital wards for the disinfection of tubercular 

 .sputum instead of mercuric chloride and other less efficacious dis- 

 infectants commonly in use. 



Hot Air and Steam. — Koch, in conjunction with WolfhUgel, also 

 made exhaustive experiments to test the value of hot air. A similar 

 plan was adopted to that employed in disinfection with chemicals. 

 Bacteria and spores were subjected for a certain time to a known 

 temperature in the hot-air chamber, and then were transferred to a 

 nourishing soil or inoculated in animals. 



Paper parcels, blankets, bags, and pillows, containing samples of 

 micro-organisms wrapped up inside, were also placed in the hot-air 

 chamber, to test the power of penetration of heat. 



The conclusions from these experiments were as follows : 



Sporeless micro-organisms at a little over 100° C. are destroyed 

 in one hour and a half. 



