170 BACTERIOLOGICAL CHEMISTRY 



Parasiticin. — A . parasiticus, when grown on a medium 

 containing peptone or 7 to 8 per cent, of corn -steep liquor 

 and small amounts of glucose at ^^H 7, gives culture fil- 

 trates which are active at dilutions of one in 200 to 600 

 against Gram-positive organisms but not against Gram- 

 negative organisms. The substance responsible for the 

 activity can be adsorbed on charcoal and eluted by 

 aqueous acetone. It has properties very similar to those 

 of penicillin and to the substances obtained from A . flavus 

 (see p. 161) and A. giganteus (see p. 163) and may be 

 identical with them. 



Patulin. — This substance is identical with clavacin 

 (see p. 160). 



Penatin. — This substance is identical with notatin 



(see p. 168). 



Penicillic Acid. — The growth of P. cydopimn on 

 Raulin's medium (but not on Czapek-Dox medium) 

 leads to the formation of about 2g. per litre of penicillic acid 



CH3 ^^^^ 



\c.CO.C =CH.COOH. It is inhibitory to staphylococci, 



E. coli and Gram -positive and Gram -negative pathogens 

 at dilutions of 1 in 30,000 to 1 in 100,000 but is only 

 poorly bactericidal. 



Penicillic acid, which is a colourless, crystalline 

 substance with m.p. 86°C, soluble in water and chloroform, 

 can also exist in a closed ring form, 



CHgO.C^^CH 



CH3 I I 



