154 BACTERIOLOGY 



sometimes be attended with considerable difficulty and doubt. In 

 the systematic study of an unknown species, the following outline 

 may prove of service: (1) Name, (2) habitat, (3) growth on me- 

 dia, (4) temperature, including that of most favorable growth and 

 the thermal death point, (5) relation of growth to oxygen, (6) 

 gas formation, (7) chemical reaction, (8) formation of indol, (9) 

 pigmentation, (10) pathogenesis, (11) aniline reaction, (12) mo- 

 tility. (13) morphology, (14) size, (15) spore formation. 



When these tests have been made, the classification may be de- 

 termined by using analytic keys, such as are found in the valuable 

 works of Sternberg and Crookshank. 



Laboratory exercise No. 51. Culture Media. Let the student prepare 

 or assist the instructor in preparing 1 the following media: Bouillon, 

 agar-agar, blood serum, nutrient gelatin, and potato medium. Make 

 inoculations upon agar-agar as directed above. The tubes should be 

 held in the left hand, between the thumb and forefinger, in such a way 

 that the palm of the hand will be vertical and the tubes but slightly 

 inclined. The cotton plugs, when removed, may be held between the 

 fingers. The greatest care should be exercised, always sterilizing the 

 platinum needle before and after using. .Make a stab-culture of some 

 anaerobic species. This is accomplished by holding the tube in a ver- 

 tical position, using a platinum wire with small loop, and plunging this 

 through the center of the medium from the surface to the bottom of the 

 tube. 



Experiments with animals. Clip the hair from the base of the tail of 

 a mouse. Make a V-shaped incision and insert into the wound some of 

 the saliva of the mouth. Saliva often contains Diplococcus pneumoniae, 

 which will cause the death of an inoculated mouse in a few hours. 

 Other inoculations may be made as desired. 



Laboratory exercise No. 52. Hanging-drop Cultures. Prepire a hang- 

 ing-drop culture upon which have been sown some spores of any species 

 of mold, such as Penicillium glaucum. After a few days examine. The 

 spores of molds may sometimes be mistaken for cocci. The hyphae, 

 or slender filaments, which compose their structure, may, when broken 

 into fragments, have some resemblance to the cells of bacilli. The 

 hyphae develop from the spores, producing three characteristic por- 

 tions the root hyphas; the mycelium, or prostrate portion; and the 

 aerial hyphae, upon the extremities of which the sporangia containing 

 the spores are developed. Also make hanging drop cultures of species 

 of bacteria, and study the same from time to time. 



Laboratory exercise No. 53. A systematic study of Bacteria. Make a 

 systematic study of Bacillus prodigiosus and other common species ac- 

 cording to the method suggested above. Fill out the outline on page 155 

 and make drawings of agar cultures and the microscopic elements. 



