APPENDIX 307 



doors where the liquid will freeze. Allow it to remain frozen for a 

 few hours, and then bring it back into a warm room, leaving it there 

 for a few days to see if it putrefies, in order to determine whether 

 freezing destroys the life of the bacteria in the hay infusion. For 

 this experiment it will be better to use a metal dish instead of a test 

 tube, since freezing might break the test tube. 



45. Effect of Boiling upon Spores. Put some hay into a dish and 

 steep with warm water at about 120°. After an hour's steeping 

 filter through filter paper into four test tubes, filling each half full, 

 plugging the same with cotton, and labeling them a, b, c, d. Bring 

 a to a boil for five minutes, b for ten minutes, c for twenty, and leave 

 d without boiling. Set aside for a few days to determine whether 

 the material in all cases putrefies. Does the hay infusion contain 

 bacteria spores that are not killed by boiling? 



46. Action of Disinfectants. Mix the white of an egg with ten 

 times its bulk of water and place the material in a series of test tubes, 

 filling each about one third full. To the tubes add the following 

 disinfectants : (a) no addition ; (b) one quarter of a gram of salt ; 

 (c) one gram of salt ; (d) one gram of sugar ; (e) five grams of 

 sugar; (f) two drops of a corrosive-sublimate solution (one part 

 sublimate to one thousand parts water) ; (g) six drops of corrosive- 

 sublimate solution ; (h) one drop of formalin ; (i) two drops of 

 formalin ; (j) three drops of formalin ; (k) one eighth of a gram of 

 borax ; (1) one fourth of a gram of borax ; (m) four drops of carbolic- 

 acid solution (one part acid to twenty parts water) ; (n) ten drops of 

 carbolic-acid solution. Set all test tubes in a warm place side by side 

 and examine daily, noticing the effect of the various ingredients in 

 pr^enting decay, and noting how much more powerful some disin- 

 fectants (corrosive sublimate) are than others (carbolic acid). Num- 

 bers h, i, j, m, and n should be closed with a cork to prevent the 

 disinfectant from evaporating. 



47. Vinegar. Soak a bit of raw meat in vinegar, warming it some- 

 what and leaving it for several hours. Remove the bit of meat, 

 placing it in a test tube plugged with cotton, and leave for a few 

 days, to determine whether it putrefies or whether the vinegar acts 

 as a disinfectant. The vinegar will prevent putrefaction if enough 

 is used. 



