14. MICROSCOPIC EXAMINATION OF BACTERIA. 
tween the thumb and finger of the left hand, allow- 
ing the lower end of the tube to rest on the back 
of the hand. 
(d) Hol& a straight platinum needle between the 
thumb and forefinger of the right hand, and ster- 
ilize it by heating red-hot. Allow it to cool. 
£ | | 
X 
Fic. 2.—Platinum needles for transferring bacteria ; made 
from No. 27 platinum wire inserted in glass rods. 
(e) Grasp the cotton plug between the third and 
fourth finger of the right hand, and remove it ; in- 
sert the platinum needle, and transfer an exceed- 
ingly minute portion of the culture of bacteria to 
the drop of water. 
(/) Return the cotton plug to the tube, and ster- 
ilize the needle.’ 
(g) Place a clean” cover-glass over the drop of 
water, and examine with the 4 inch objective. 
1 The needle should invariably be heated before and after 
_using. If this practice is not carefully followed, cultures 
will be contaminated, and perhaps pathogenic organisms 
spread about the room. It is well also to pass the handle 
of the needle through the flame before beginning work 
each day. 
? Cover-glasses and slides may be cleaned in the follow- 
ing solution : 
Potassium bichromate, 6 gm. ; 
Concentrated sulphuric acid, 6 c.c. ; 
Water, 100 ¢c.c. 
Wash in water and store in alcohol. 
Or boil the cover-glasses in sulphuric acid, wash in 
