PHYSIOLOGY OF THE MICROBES 77 



We know how to prepare a clean vaccine fluid by culture 

 on the flanks of the calf, but we cannot prepare in vitro a vaccine 

 lymph bacteriologically pure. This would be possible if we 

 knew the nutritive demands of the vaccine virus. This virus 

 is a microbe still unknown, but probably living in the interior of 

 the epidermal cells ; it finds itself there in a medium in which 

 reducing actions predominate. Rdpin succeeded in preparing 

 a reducing medium by means of a living reducing agent put 

 into a culture flask (the tyrosinase extracted from the 

 mushrooms of the genus Russula) ; with this he got a 

 commencement of growth in the vaccine under artificial 

 conditions. It is obvious what problems lie in wait for those 

 who try to grow bacteria in the laboratory. 



The Nutrition of Yeasts. — The yeasts are of such great 

 industrial value that every detail of their nutrition has had to 

 be studied. They demand phosphoric acid and potassium, 

 magnesium, lime, and sulphur; their nitrogenous food they take 

 from ammoniacal salts and they can use those albuminoid 

 substances which are soluble in water, dialysable, and more or. 

 less insoluble in alcohol, and which exist in serum ; also they 

 can use urea and allantoin. The carbohydrates they employ 

 are in the first place sugars, then various alcohols, acids and 

 organic salts. From its food the yeast accumulates reserve 

 material, i.e., glycogen. Yeast attacks the food-stuffs supplied 

 to it by means of its diastases ; and in doing so, while toiling 

 for its own purposes, it toils for ours — exactly like a hive of bees. 



Alimentation of Bacteria. — The minerals employed in 

 nutrition are rather varied ; sulphur, phosphorus, calcium, 

 magnesium, potassium, sodium, traces of iron, traces of chlorine. 

 As carbohydrate food, sugars and glycerine; as nitrogenous, 

 ammoniacal salts and peptones, natural proteins like blood 

 serum and asparagine. The food-stuffs are supplied by meat 

 infusions, bouillons with peptone and salt, by animal fluids such 

 as serum, urine, ascitic fluid, milk, and by fruit juices. The 

 preferences which bacteria show for certain foods are employed 

 for diagnosis, because bacteria are characterised not less by 

 their food preferences than by their shape. 



