352 SCIENCE OF HOME AND COMMUNITY 



Molds in the Home. It will be convenient to melt the culture 

 and fill a number of sterilized test tubes about half full. Plug 

 each tube with cotton batting. 



2. Obtain several samples of water, some from the faucet, 

 some from a well, some from bottled water, some from melted 

 snow, some from a river, some from the street gutter. 



3. Take as many culture tubes as the samples of water to 

 be tested, place them in a dish of water and heat the water till 

 the gelatin melts. By means of a sterilized pipette introduce 

 i cc. of the samples of water into the various tubes, one tube 

 for each sample. Shake the tubes so as to mix thoroughly the 

 water and pour the culture medium from each tube into a 

 sterilized petri dish, covering at once. Put a piece of gummed 

 paper on each dish and label the source of the water. 



4. Allow to remain at ordinary temperature for two or three 

 days. Count the number of colonies which appear. This 

 represents the number of bacteria in the cubic centimeter of 

 water. Which sample contained the most ? Which the least ? 



Milk. Milk is one of the best foods that we have. But 

 it is also a medium most favorable to the growth of bacteria 

 and great care should be taken to see that milk is clean. 

 Milk is a common means of carrying disease germs and pro- 

 ducing epidemics. An investigation made by the surgeon- 

 general of the army showed that at least 500 epidemics in 

 this country had been traced to impure milk. Of these epi- 

 demics, 317 were of typhoid fever, 125 of scarlet fever, and 

 51 of diphtheria. Tuberculosis and tonsillitis germs also 

 may be carried by milk. It is thought that one sixth of 

 the cases of typhoid fever are due to unclean milk. 



How milk may carry diseases. Cows may have tubercu- 

 losis, in a form similar to that found in man, and these 

 cows may be a means of giving the disease to man directly 

 through milk and meat. But most of the disease germs 

 found in milk are introduced through carelessness after it 

 is drawn from the cows. Some epidemics of typhoid fever 



