THE ART OF SCIENTIFIC INVESTIGATION 



this disease, refractory to other forms of treatment, could in 

 most cases be cured by the simple expedient of fasting for a 

 few days. 



(17) Paul Ehrlich's discovery of the acid- fast method of stain- 

 ing tubercle bacilli arose from his having left some preparations 

 on a stove which was later inadvertently lighted by someone. The 

 heat of the stove was just what was required to make these 

 waxy-coated bacteria take the stain. Robert Koch said " We 

 owe it to this circumstance alone that it has become a general 

 custom to search for the bacillus in sputum." ^^^ 



(18) Dr. A. S. Parkes relates the following story of how he and 

 his colleagues made the important discovery that the presence of 

 glycerol enables living cells to be preserved for long periods at very 

 low temperatures. 



" In the autumn of 1948 my colleagues. Dr. Audrey Smith and 

 Mr. C. Polge, were attempting to repeat the results which 

 Shaffner, Henderson and Card (1941) had obtained in the use of 

 laevulose solutions to protect fowl spermatozoa against the effects 

 of freezing and thawing. Small success attended the efforts, and 

 pending inspiration a number of the solutions were put away in 

 the cold-store. Some months later work was resumed with the 

 same material and negative results were again obtained with all 

 of the solutions except one which almost completely preserved 

 motility in fowl spermatozoa frozen to -79 °C. This very curious 

 result suggested that chemical changes in the laevulose, possibly 

 caused or assisted by the flourishing growth of mould which had 

 taken place during storage, had produced a substance with sur- 

 prising powers of protecting living cells against the effects of 

 freezing and thawing. Tests, however, showed that the mysteri- 

 ous solution not only contained no unusual sugars, but in fact 

 contained no sugar at all. Meanwhile, further biological tests had 

 shown that not only was motility preserved after freezing and 

 thawing but, also, to some extent, fertilizing power. At this point, 

 with some trepidation, the small amount (10—15 ml.) of the 

 miraculous solution remaining was handed over to our colleague 

 Dr. D. Elliott for chemical analysis. He reported that the solution 

 contained glycerol, water, and a fair amount of protein ! It was 

 then realised that Mayer's albumen — the glycerol and albumen 

 of the histologist — had been used in the course of morphological 

 work on the spermatozoa at the same time as the laevulose solu- 

 tions were being tested, and with them had been put away in the 

 cold-store. Obviously there had been some confusion with the 

 various bottles, though we never found out exactly what had 



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