90 Perspecf'iYes in Microbiology 



among organisms which are morphologically indistinguish- 

 able. The existence in microorganisms of evolutionary 

 divergence of morphology and of metabolic patterns for 

 securing energy is regarded as elementary in modem mi- 

 crobiolog)^ Yet, it was in his studies on the fermentative 

 tendencies of filamentous fungi that Pasteur, more than 

 three quarters of a century ago, made apparently the first 

 definitive observations on the existence of strain specificity, 

 which he called "physiological polymorphism." 



Here, too, we may mention the very beginnings of ex- 

 perimental studies on trace-element nutrition, employing 

 the ubiquitous mold Aspergillus niger as the test system. 

 To these studies, published in 1869 by J. Raulin, who was 

 Pasteur's first doctoral student, may be traced the elegant 

 modern studies on trace-element function in enzyme 

 action. 



Although the record shows that the aforementioned his- 

 torical studies on fungi, as well as many others which 

 could be cited, stand clear in their anticipation of later 

 developments, it would be poetical to assume that they 

 were directly responsible for the revolutionary develop- 

 ments occurring much later. I prefer to think that, how- 

 ever well documented, the metabolic studies on fungi in 

 the early days made little impact on general biology be- 

 cause they were regarded as unique to that particular group 

 of organisms, the fungi, which were virtually unknown to 

 investigators not specializing in them. Only much later, 

 when the particular metabolic phenomena were rediscov- 

 ered in plant tissue, in animal tissue, in bacteria, and in 

 yeast, were they exploited, and the significance of the early 

 fungus studies acknowledged through courtesy of hind- 

 sight. 



One may well wonder what the state of our knowledge 

 in certain areas might have been today had certain 

 phenomena, first recognized in fungi long before their 

 modern culmination, been assiduously exploited when 



