26 



Metastable Solutions of Inorganic Colloids. 



granular matter resembling protoplasmic debris, and leaves tbe long fibres 

 and shorter nests of exquisitely fine fibrils more clear. 



In the appended microphotographs are shown growths from these and 

 other tubes of the series. 



These growths, obtained in hermetically sealed tubes, autoclaved up to 

 110-116° C. after sealing, and in tubes in which all organic matter must have 

 been completely destroyed in the process of manufacture, appear to us to be 

 proven conclusively not to be caused by any contamination with adventitious 

 organisms. Whatever view may be taken as to the nature of these appear- 

 ances, our opinion is that they are not adventitious or due to contamination, 

 but that they arise de novo in the tubes by a process of growth or deposition 

 from the balanced colloids. 



While the boiling or autoclaviug was essential in the first stages of the 

 investigation in order to rule out contamination, this process undoubtedly 

 disturbs to a great extent the metastable condition of the colloids and throws 

 out a good deal of the substances, and, in addition, probably interferes with 

 the labile condition of the remainder short of actually precipitating it. 



In order to get rid of this inactivation by heat, it was determined, after the 

 growth in autoclaved solutions had once been settled, to experiment with 

 tubes containing metastable colloidal systems which had only been exposed 

 to a moderate degree of heating so as not to disturb any thermo-labile 

 colloids present. The result was that much more growth occurred of all the 

 constituents described. 



A series of tubes, filled as described above, were prepared in April, 1914 ; 

 but, instead of autoclaving, these tubes were heated for 20 minutes to 50° C. 

 and then allowed to stand for two months. At the end of the period, this 

 set of tubes showed very little deposit, but the forms found in the deposit 

 were beautifully developed. 



It is to be remembered here that none of the tubes contained any nutrient 

 materials for ordinary micro-organisms, and that heating to 50° C. for 

 20 minutes would have destroyed any common forms likely to be present. 

 The forms, moreover, closely resembled those found much more sparsely in 

 the autoclaved tubes, and the explanation of the abundance appears to lie in 

 the fact that the colloids were left in a more labile condition. 



It is admittedly impossible to exclude completely the objection of con- 

 tamination in this latter series of experiments. Other methods of causing 

 metastability in mixtures of inorganic colloids and so producing growths 

 more rapidly have been studied and are described in the succeeding paper. 



