SERUM MEDIA FOR GONOCOCCUS 43 



of these media, sterilisation is effected by method B (4), and 

 they are used fluid. 



Serum Media for Gonococcus. — The following media will be 

 found suitable : — 



Wertheim's Medium consists of one part of sterile human serum and 

 two parts of peptone agar. The agar is melted in tubes and allowed to cool 

 to 45° C. ; the serum warmed to the same temperature is then added, and 

 the mixture is allowed to solidify in the sloped position. Human serum 

 may he conveniently obtained from placental blood or from blood drawn 

 off for the Wassermann reaction. 



Gurd's Medium is a 2 per cent, agar with aeid reaction + 6 to phenol- 

 phthalein (p. 34), with defibrinated human blood added in the proportion 

 of about 5 drops to 5 c.c. of agar ; the blood is added to the melted agar 

 as in Wertheim's medium. W. B. M. Martin recommends the substi- 

 tution of sodium phosphate ('5 per cent.) for sodium chloride in the 

 preparation of the agar, and uses fluid human serum sterilised at 57° C. 

 in place of blood. He also finds that the same agar medium allowed to 

 solidify and then smeared on the surface with a drop or two of human 

 serum or blood gives excellent results. 



Thomson's Medium. — This is an agar medium with the addition of 

 human plasma. Nutrient agar (2 '5 per cent.) is prepared in the usual 

 way from meat juice with 1 per cent, of Witte's peptone added and 

 its reaction brought to +6. But instead of the usual 0'5 per cent, 

 sodium chloride, the salts of Ringer's solution are added, namely, sodium 

 chloride 9 grms., calcium hcloride 0'25 grm., and potassium chloride 

 '42 grm. , per litre. Glucose in the proportion of 2 '5 per cent, .is also 

 added. The medium is then sterilised and tubed — 4 c. c. in each tube. 



To obtain the plasma a tubeful of human blood is drawn off as for a 

 Wassermann reaction. About 10 c.c. are poured at once into a centrifuge 

 tube containing 2 c.c. of a 2 per cent, of sodium chloride solution, to 

 prevent clotting, and fitted with a sterile cork. The blood is then 

 centrifuged till the corpuscles are thrown down. The agar medium in 

 tubes is melted and its temperature brought to 50° C. To each tube is 

 then added with a sterile- pipette 1 c.c. of plasma, and the mixture is 

 allowed to solidify in the sloped position. The medium gives a very 

 abundant growth, and is very suitable for the preparation of vaccines. 



Any of these media may be used for plate cultures, the agar 

 being melted and cooled to 45° C. as for agar plates ; the serum 

 or blood is then added, and the mixture is poured out in Petri 

 dishes. 



Medium for Meningococcus. — Trypagar. — Gordon has introduced 

 this medium for the cultivation of the meningococcus. It is prepared 

 as follows : — 



1. Take 50 grms. of pea flour (ordinary Pearce Duff's) and add to 1 litre 

 of distilled water with 100 grms. of salt. Mix and steam for half an 

 hour, stirring occasionally ; allow to settle, and filter, then sterilise and 

 label "Saline Pea Extract." This pea extract should preferably be 

 freshly made for each batch of agar. 



2. Take some fresh bullocks' hearts, free from fat and vessels, mince 

 the meat very finely, and weigh. To each £ kilo add 1 litre of water, 



