244 FLEAS, FLUKES AND CUCKOOS 



has been recorded from several common birds on the British list 

 such as the blackbird and sparrow, and there seems little reason to 

 doubt that it will eventually be found in this country. 



The relationship which exists between parasitic fungi and bacteria is 

 one of the greatest interest. In many cases these two types of organism 

 compete with one another in the same environment. Often the presence 

 of bacteria in a culture of fungi arrests its development, but in other 

 cases they seem to exert a beneficial influence. Certain Staphylococci, 

 for example, stimulate the growth of Achorion^ and in the presence of 

 bacteria (but not in pure cultures) Aspergillus produces spore-bearing 

 perithecia. On the other hand it is now known that extracts of 

 certain fungi have a powerful antibiotic or lethal effect on various 

 bacteria. In 19 13 Vaudremer showed that a filtered extract o^ Asper- 

 gillus fumigatus inhibited the growth of tubercle baciUi. In recent years 

 penicillin has been extracted from various species of Penicillium 

 (especially P. notatum) and has proved the most powerful antibiotic ever 

 known. An extract from another fungus, Streptomyces griseus, now known 

 as streptomycin, also exerts a powerful lethal effect on certain bacteria, 

 among them species such as the tubercle bacillus, which is not affected 

 by penicillin. The secretions of fungi have consequently provided one 

 of the great discoveries of the age. 



