BACTERIOLOGICAL TECHNIC 37 



Glycerin egg medium. Add 6 per cent glycerin to 

 the egg mixture before heating. 



Glycerinated potato. Prepare potatoes in the usual 

 manner and soak for 24 hours in a 25 per cent glycerin 

 solution in distilled water. 



Substitute for glycerinated potato. Mix 6 per cent 

 glycerin with the substitute for potato described on p. 

 29. 



EXERCISE 1 6. PREPARATION OF EGG MEDIA 



Dorset's egg medium. Eggs are broken into a 

 flask and the yolks broken with a platinum needle or 

 glass rod. The flask is gently shaken until the yolks 

 and whites are thoroughly mixed. Foam formation 

 should be avoided. Distribute in culture tubes and 

 sterilize in a Koch inspissator or autoclave in the same 

 manner as blood serum. 



Dorset's egg-yolk medium. Add 5 to 10 c.c. of 

 sterile distilled water to the yolks of three or four eggs, 

 and treat the same as in the above egg medium. 



Capaldi's egg medium. A few loopfuls of egg yolk 

 are added to a tube of liquefied agar, previously cooled 

 to 45 to 47 C. 



EXERCISE 17. MEDIA FOR THE STUDY OF SOIL 

 BACTERIA 



Winogradsky's solution 



MgSO 4 o . 50 gram 



CaCla o.oi gram 



NaCl 2 . oo grams 



Distilled water 1,000 c.c. 



