524 SA GTEBIOL OGY. 



eight, and seventy-two hours. No growth occurs. How 

 is this to be accounted for? 



At the end of seventy-two hours inoculate all of these 

 plates with a culture of the same organism which has 

 not been exposed to sublimate, by taking up bits of cul- 

 ture on the needle and drawing it across the plates. A 

 growth now results. We have here an experiment in 

 which organisms which have been exposed to sublimate 

 for a much shorter time than necessary to destroy them, 

 when transferred directly to a favorable culture medium 

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

 not been exposed to sublimate at all is planted upon the 

 same medium it does grow. How is this to be ac- 

 counted for ? 



Skin-disinfeotion. 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 some one pour am- 

 monium sulphide over the points from which the scrap- 



