64 



§ 104. Making cover-glass preparations from tissues. 



With a pair of fine forceps take up a bit of tissue from the 

 freshly cut liver, spleen or kidney and rub it gently over the 

 surface of a clean cover-glass. Care must be taken that the 

 film of tissue left on the cover-glass is thin. Allow this to 

 dry in the air after which pass them three times through the 

 flame to fix the film to the glass. They can be stained the 

 same as the cover-glass preparations from the cultures. 

 These are often spoken of as smear preparations. 



In making these preparations from blood, hold a cover- 

 glass by the edge with a pair of dissecting forceps. Place a 

 drop of blood with the platinum loop on the cover-glass near 

 the forceps. Take a thick, square cover-glass by the edge, 

 rest it on the first above the drop of blood, hold it at an 

 angle of about 20'' from it and draw it down over the first 

 thus spreading the blood in a very thin even film over the 

 surface. If the film is thick the preparation should be re- 

 jected and another one made. 



EXERCISE XXXIII. 



BACII.LUS CHOLERAE SUIS AND BACILLUS TYPHOSUS 

 (continued). 



§ 105. Re-examine and complete the notes on all of the 

 cultures except the milk and litmus milk which should be 

 kept for 3 weeks longer. Carefully observe the reaction of 

 all the liquid cultures. 



Stain the flagella on the bacteria from the agar cultures 



(§72)- 



Compare the colonies on the gelatin plates with those of 

 B. coll communis. 



Make a careful comparison, in tabulated form, of the 

 morphology, including measurements, of the bacilli them- 



