II] PREPARATION OF CULTURE MATERIAL 31 



temperature of 58° to 62° C. in the same manner and for 

 the same tnne as the hydrocele fluid was. 



Blood of ox or sheep obtained in the slaughter-house is 

 the blood from which generally " serum " is obtained ; it is 

 received into sterile glass vessels, and treated in the same 

 way as just described. 



6. Urine is neutrahsed and sterilised by boiling for 20 to 

 30 minutes like broth. 



7. Milk (pure or better separated) is sterilised by gentle 

 and careful steaming for 20 to 30 minutes on three succes- 

 sive days. 



8. Whey is now also used as such, or better as an admix- 

 ture to gelatine or agar ; in either case it can be easily 

 sterilised by steaming. 



Of less common use are : — 



9. Pasteur's Fluid. — In 100 parts of distilled water are 

 dissolved 10 parts of pure cane-sugar, i part of ammonium 

 tartrate, and the ash of i part of yeast. 



10. Cohiis Fluid. — 100 ccm. of distilled water, i gramme 

 of ammonium tartrate, no sugar, and instead of the ash of 

 yeast are substituted (A. Mayer) o'5 gramme of potassium 

 phosphate, or o'5 gramme of crystallised magnesium sul- 

 phate, o'o5 gramme of (tribasic) calcium phosphate. These 

 two fluids are sterilised in the same manner as the broth 

 and peptone solutions. Pathogenic organisms do not thrive 

 in either of these two fluids. 



j9.— Solids. 



The solid media have the great advantage over the fluids 

 that in the former artificial cultures can be carried out more 

 easily ; as, owing to the resistance the solid basis offers to 



