SIMPLE BACTERIOLOGY FOB PUBLIC SCHOOLS. 47 7 



was placed in a sterile glass vessel and allowed to clot. After stand- 

 ing some time, serum separated. One cubic centimeter of this serum 

 was placed in a small test-tube and five loops full of a beef-broth cul- 

 ture of typhoid bacilli were added to it. Petri dishes were made from 

 this mixture at intervals for an hour. To get an idea of the number 

 of germs originally placed in the serum, a control was run with 1 c.c. 

 of sterile water. The count made from this control is recorded as the 

 count for minutes. 



minutes 3,760 colonies. 



2 



8 



15 



30 



60 



737 



410 



34 



2 







12. To show that Bacteria are not given off from a Moist Surface. — 

 A culture of harmless, brilliant yellow bacteria was smeared on the in- 

 side of a large glass tube. Through this tube a strong current of air 

 was directed on to agar in a Petri dish. If bacteria were given off 

 into the air from the moist surface, they would be blown upon the 

 agar, where they would develop into colonies. The Petri dish used 

 in this experiment developed no yellow colonies. The smear was now 

 allowed to dry and was then crushed with a sterile glass rod. A second 

 current of air was now directed through the tube into another Petri 

 dish. This dish developed 240 colonies of yellow bacteria. 



The above is merely suggestive of the kind of work that might be 

 done in any secondary school. Most of these experiments could be 

 performed by the average high school senior. All of them could be 

 used as class demonstrations. Each one has a direct bearing on some 

 large question of preventive medicine. A week's training in bacteri- 

 ological technic will enable any teacher to give this work. 



The experiments here outlined were suggested to me by Dr. W. H. 

 Manwaring, and were carried out in the Pathdlogical Laboratory of 

 the University of Chicago, during the summer of 1904. 



