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 16. 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 4S to 47° C. 



EXERCISE 17. MEDIA FOR THE STUDY OF SOIL 

 BACTERIA 



Winogradsky's solution — 



MgS04 0.50 gram 



CaCU o.oi gram 



NaCl 2.00 grams 



Distilled water 1,000 c.c. 



