39 



(2) in stained cover-glass preparations. Stain a preparation 

 with carbol fuchsin and one with an aqueous solution of 

 gentian-violet. Describe the appearance of the bacteria 

 ( 33) and make a drawing of a few of them. 



59. A few points to be observed in studying cultures 

 on special media, (a) Potato. Note carefully the extent 

 and color of the growth and also its consistence. 



() Milk. Note whether or not the general appearance 

 and odor of the milk has been changed, observe whether 

 the casein has been coagulated giving a firm solid coagulum, 

 or precipitated. Is the coagulum covered with a liquid 

 (serum), if so, is it clear or milky? Is there any appear- 

 ance suggestive of saponification. Determine its consist- 

 ence, chemical reaction as indicated by litmus paper ( 24), 

 and give as descriptive a name as possible to its odor. 



(c) Litmus milk. Note especially whether there has been 

 any change in color since inoculation. Observations similar 

 to those on the plain milk should also be made. 



(d) Glucose agar. Note the character and number of 

 colonies within the agar, and the presence, if any, of gas 

 bubbles. Are there few or many of them ? 



(*) Glucose bouillon. Observe the character of the growth 

 (whether the liquid is faintly or heavily clouded, turbid, 

 contains flakes, etc.) in (i) the open branch and (2) the 

 closed branch of the fermentation tube. Note the presence 

 or absence of a membrane on the surface of the liquid in 

 the open bulb. Is there a sediment in the bottom of the 

 tube ? If so, describe its general appearance and consist- 

 ence. Note the presence or absence of gas in the closed 

 branch. Indicate the quantity. Test the reaction of the 

 liquid with litmus paper. 



(/) Lactose and saccharose bouillon. Same as glucose 

 bouillon. These cultures should be observed from day to 

 day and note made of any changes which have occurred. 



