MORPHOLOGY, KINDS, AND PRODUCTS. 147 



rose-color indicates the presence of indol and nitrites. Should no 

 rose-color appear, another tube should be tested, adding, first, 1 c. c. 

 of .01 per cent solution of sodium nitrite, and then the sulphuric 

 acid. The formation of a rose-color indicates the presence of indol 

 alone. 



Laboratory exercise No. 47. Morphology. Make cover-glass prepara- 

 tions of species of cocci, bacilli, and spirilla. Note the peculiar form 

 of the individuals of each species. To demonstrate the different kinds 

 of cocci, the following species may be used: Micrococcus urese, Diplo- 

 coccus pneumonias, Sarcina lutea, Streptococcus pyogenes, Staphylococ- 

 cus pyogenes aureus, and Ascococcus Billrothii. 



Apply to the surface of a cover-glass some of the scrapings obtained 

 from the teeth just under the gums. Cover this with another glass and 

 by pressure spread out the material so as to make a thin film. Dry, fix, 

 and stain. (See method No. 10.) Examine your preparation and ob- 

 serve cocci, spirilla, and bacilli. Note the large ribbon-like forms, 

 which probably represent LeptotJirix buccalis. Make drawings to illus- 

 trate a]l of these forms. 



Laboratory exercise No. 48. Motility. Apply to a clean slide some 

 of the scum upon the surface of hay infusion. Cover and note the slen- 

 der filaments made up of rod-like cells. Each cell represents an indi- 

 vidual of Bacillus subtilis. Observe the slow, gliding motion of the fila- 

 ments. How is this motion secured? Look for other bacteria. Some 

 may be found with a vibratory motion. If this motion is confined to 

 one place without producing any progress across the field of vision, it 

 is purely physical, the so-called Brownian movement. 



Laboratory exercise No. 49. Products. Fill the long arm of the Sac- 

 charometer with bouillon and inoculate the medium with some zymogenic 

 species. The formation of gases in the upper end of the arm indicates 

 the action of the bacteria. Make the test for indol, as described above, 

 using as a culture-medium Dunham's Peptone solution, which is pre- 

 pared by boiling, filtering, and sterilizing a mixture of 10 grams of pep- 

 tone, 5 grams of sodium chloride, and 1 liter of water. 



