256 BACTERIOLOGY. 



them, when transferred directly to a culture medium do 

 not grow, and yet, when the same organism which has 

 not been exposed to sublimate is planted upon the same 

 medium it does grow. How is this to be accounted for ? 



SKIN-DISINFECTION. With a sterilized knife scrape 

 from the skin of the hands, at the root of the nails and 

 under the nails, small particles of epidermis. Prepare 

 plates from them. Note the results. 



Wash the hands carefully for ten minutes in hot 

 water and scrub them during this time with soap and a 

 sterilized brush. Rinse them in hot water. Again prepare 

 plates from scrapings of the skin on the fingers, at the 

 root of the nails, and under the nails. Note the results. 



Again wash as before in hot water with soap and 

 brush, rinse in hot water, then soak the hands for five 

 minutes in 1 : 1000 corrosive sublimate solution, and, as 

 before, prepare plates from scrapings from the same 

 localities. Note the results. 



Repeat this latter procedure in exactly the same way, 

 but before taking the scrapings let someone pour am- 

 monium sulphide over the points from which the scrap- 

 ings are to be made. After it has been on the hands 

 about three minutes again scrape and note the results 

 upon plates made from the scrapings. 



Wash as before in hot water and soap, rinse in clean 

 hot water, immerse for a minute or two in alcohol, after 

 this in 1 : 1000 sublimate solution, and finally in am- 

 monium sulphide, and then prepare plates from scrapings 

 from the points mentioned. 



In what way do the results of these experiments differ 

 the one from the other ? 



To what are these differences due ? 



What have these experiments taught ? 



