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Note on the Nature of Growths in Colloidal Silica Solutions. 

 By H. Onslow, Trinity College, Cambridge. 



(Communicated by Professor F. G. Hopkins, F.R.S. Received March \, 1918.) 



The late Dr. Charlton Bastian,* after having performed a number of 

 experiments, claimed to have synthesised certain symmetrical bodies 

 resembling torulee and other minute organisms, from sterilised colloidal 

 solutions which had been exposed for a long period to the light. Further, 

 he claimed that such " organisms " were capable of reproducing themselves. 



In spite of the inherent improbability of these results, Dr. Bastian was so 

 insistent in his claims, and so anxious for independent investigation, that 

 I undertook to repeat his experiments carefully, in order to ascertain 

 whether the organised bodies in question were in reality living proto- 

 plasm. 



The difficulty of proving a negative is obvious, but it is hoped that the 

 following experiments, taken in conjunction with recent workf in the same 

 field, may help to decide whether the forms observed by Dr. Bastian were, as 

 I now believe, colloidal simulacra, or no. 



The existence of living organisms can be most conclusively proved by sub- 

 cultivation in media that have previously been shown to be sterile. The 

 procedure adopted was therefore based on this principle. The media used 

 consisted of: (1) Dr. Bastian's neutral ammonium tartrate and sodium 

 phosphate solution ;| (2) ordinary sterile nutrient broth ; and (3) " tryptic 

 broth," a special medium recently described by S. W. Cole and the author. § 

 This medium is prepared from a solution of casein digested with trypsin, and 

 was adopted after Dr. Bastian had stated|| that the addition of a trace of 

 tyrosine greatly increased the number and the rate of growth of the 

 organisms, as well as the positive results. " Tryptic broth " contains 

 not only a considerable amount of tyrosine, but of other amino-acids as 

 well, and is therefore particularly favourable to the growth of micro- 

 organisms. 



A series of 90 tubes was prepared, using three different samples of 

 * ' The Origin of Life, etc.,' by H. Charlton Bastian, F.E.S. 



t B. Moore and J. A. Webster, ' Eoy. Soc. Proc.,' B 593, p. 163 (October, 1913) ; 

 B. Moore, ' Eoy. Soc. Proc.,' B 609, p. 27 (July, 1915). 



X 'The Origin of Life ' (2nd edit.), by Dr. Charlton Bastian, p. 40. 



§ 'Lancet,' July 1, 1916. 



II 'Nature,' p. 537, July 15, 1915. 



