202 PATHOGENICrTY; CHEMOTHERAPY 



of the blood-stream. SulphaguaDidine is comparatively 

 insoluble, is scarcely absorbed from the gut and consequently 

 finds use as an intestinal disinfectant. The sulphonamides 

 act by competing with ^-amino-benzoic acid in some essential 

 metabolic path in the organism (see Chap. V). 



y Y s CH 



HzN/ yS0^HH^ y ^ | || 



N / HzN/ ysOz — HH — C CH 



SULPHANILAMiDE 



SULPHATHIA20LE 

 /NH2 

 H,U{ >S02-N=C 



^NH2 



SULPHAGUANIDINE 



Marfanil, etc. : Marfanil is ^-sulphonamido-benzylamine, 

 but its action appears to bear no relation to ^-amino-benzoic 

 acid metabolism, as it is not antagonised by this substance and 

 sulphonamide resistant organisms are sensitive to marfanil. 

 It is more effective than the sulphonamides in the presence of 

 pus, but is non-effective on injection, probably since it is 

 decomposed by the amine oxidase of body tissues. Derivatives 



H^N— CH2— ^~^— SO2NH2 



Marfanil 



in which the amino- and amido-groups are substituted prove 

 effective against the Clostridia. 



AcRiDiNE Derivatives: certain mono- and di-amino- 

 acridines, such as proflavin, acriflavin, etc., are active in high 

 dilution against Gram-positive bacteria and, to a less extent, 

 against Gram-negative organisms. They are relatively non- 

 toxic to man. Since acridines combine with nucleotides, it is 

 thought that these substances interfere with coenzyme 

 systems of bacteria and so block certain metabolic paths. 

 Their use, other than for superficial appUcation, has been 



