70 



A MANUAL OF BACTERIOLOGY 



filter through paper. Add sufficient water to the filtrate 



to make up to 1,000 c.c. 



Nutrient beef -broth. Constituents : 1,000 c.c of acid 



beef -broth ; 10 grm. of peptone ; l 5 grm. of sodium 



chloride. 



Nutrient " Lemco "-broth. Constituents : Lemco, 10- 



20 grm. ; peptone, 10-20 grm. ; sodium chloride, 5-10 

 grm. ; water, preferably distilled, 

 1,000 c.c. 



In either case, boil over a water- 

 bath or steam in the steam-steriliser 

 until the constituents are completely 

 dissolved. Then neutralise or stan- 

 dardise (p. 64). Again heat over 

 the water-bath or in the steamer for 

 half an hour, then filter through two 

 thicknesses of coarse filter - paper. 

 The broth should now be quite clear 

 and bright, but if it should filter at 

 all cloudy, cool to 50 C., add the 

 white of an egg beaten up with the 

 shell, and heat for half an hour, filter, 

 tube, or keep in bulk, and sterilise. 

 (For the preparation of dextrose-free 

 broth see p. 32.) 



Trypsin-broth. To avoid the use 

 of prepared peptones, Douglas 2 



devised a medium made from meat and trypsin. 



A fresh average-sized bullock's heart is obtained and 



freed from fat and the large vessels. The meat is 



then finely minced and four litres of water are added 



1 Witte's peptone was formerly almost exclusively used, but is now 

 unprocurable. Fairchild Bros, make an efficient substitute, or Douglas's 

 trypsin broth may be employed. The French " Peptone Chapoteaut " is 

 another form. 



2 Lancet, 1914, vol. ii, p. 891. 



ABC 



FIG. 9. Tubes of cul- 

 ture media. A. Up- 

 right agar. B. Potato, 

 c. Sloping agar. 



