6 OPENING ADDRESS 



convincing, and I conceded defeat quickly so that we could go sight- 

 seeing. Soon a long publication appeared in which van Niel explained 

 every one of my experiments according to his views. 



My experiments were perfectly reproducible. But except for some 

 evidence that the photochemistry with aliphatic acids was much more 

 complex than the simple overall equation of green plant photosynthesis 

 allowed for, I had no rational hypothesis at all. It was only a few years 

 later, after Hill's chloroplast reactions and mainly on account of my 

 own photo reduction experiments, that I understood fully the power of 

 van Niel's concept. Because I firmly believe that the mere description 

 of new phenomena is the lesser half of any scientific task and that 

 facts, unless they can be used to supporter to revise current theoret- 

 ical opinion, remain just memorable curiosities until someone pro- 

 vides the theoretical connection with existing knowledge, I would like 

 to point out the following. Considering that van Niel's was the first 

 comprehensive and fruitful theory of photosynthesis which had been 

 proposed until that time, he had to make the attempt to keep the funda- 

 mental principle intact. 



It has been very agreeable, satisfying, and flattering, of course, 

 that recently Stanier and Doudoroff did prove that the reactions in 

 purple bacteria I had written about really exist. And I can only recom- 

 mend warmly the technique of staying alive long enough to see such 

 vindications happen. But does this invalidate van Niel's general con- 

 cept of photosynthesis as it applies to the metabolism of purple bac- 

 teria? I do not think so for a moment. 



Here I would like to digress with a remark on the importance of 

 schools and the influence of masters. When I first met van Niel in 

 1935 I was absolutely under the spell of Warburg. He was twenty years 

 older, in the prime of his productivity with a dozen fundamental dis- 

 coveries already to his credit and many more ahead of him. He was 

 then an implacable foe of Wieland's dehydrogenation theory. He be- 

 lieved (as most of you are well aware he still does) in the direct 

 photochemical decomposition of carbon dioxide, and this was sufficient 

 to put a block into my brain. The Wieland-Kluyver-van Niel way of 

 looking at the same factual material I rejected for reasons only a 

 psychologist may be able to explain to us in the future. I tell this story 

 because the same strange power is, as you know, still at work today. 

 And it means that conscientious teachers should, after having convinced 

 their pupils of their own viewpoint, challenge them to find faults with 

 the ruling theory of the laboratory and help them even in this exercise. 



Another digression is on the lucky choice of material to work with. 

 If Willstatter and Stoll had studied minced spinach extracts instead of 

 minced sunflower leaves they might have found what Hill found twenty 

 years later. The fabulous success of Warburg's choice of Chlorella we 

 need only to mention in passing. If I had started with Chromatium in- 

 stead of with Athiorhodaceae the confusing conflict with van Niel might 



