H. B. HrTCKiNSON and J. Olayton 155 



raation and persistence of spoioids tend to become accentuated with 

 increasing age of the culture until, at the end of two to three weeks, the 

 whole of the bacterial mass and also of the partially decomposed cellulose 

 fibres appear to consist exclusively of micrococci. This was, no doubt, 

 the phase observed by van Iterson, who refers to the fibres as being 

 embedded in "micrococcus mucilage." 



Until the organism has been subjected to further study by the use of 

 special cytological methods it would be premature to express any 

 opinion as to the significance of the changes which the organism under- 

 goes. It is hoped that sufficient evidence ha.s been already adduced to 

 indicate the complexity of these changes. 



Physiological. 



On account of the difficulty of separating the filamentous and the 

 sporoid forms of the organism and, incidentally, of estabhshing their 

 relationship to one another, we recognised at an early date the desir- 

 abiHty of obtaining some synthetic medium suitable for the preparation 

 of hanging-drop cultures and on w'hich continuous observations of the 

 organisms would be possible. With this end in view it was decided to 

 investigate systematically the relative value of various forms of nitrogen 

 and carbon. 



As is shown by the results of the experiments reported below, 

 Spirochaeta cytophaga is markedly specific in its nutritive requirements; 

 at the same time it displays extraordinary sensitiveness towards the 

 presence of compounds which it is apparently unable to utiUse but which 

 with the general run of bacteria have been found to serve as sources 

 of nitrogen or carbon or both — peptone, amino-acids, sugars, salts of 

 organic acids, etc. Since the organism invariably grows well in mineral 

 salt solution with cellulose, the general method adopted in systematic 

 tests was to prepare a range of test tubes having the same basal mineral 

 salt solution, but with different, and sometimes increasing, amounts of 

 carbon or nitrogen compounds. According as to whether cellulose was 

 also present or absent, it was possible to ascertain {a) inhibitive effects, 

 and (b) nutritive values of the compound tested. 



In the summary of these experiments recourse is had to tabular 

 representation of the results; the individual cultures are arranged as a 

 rule in order of gradually increasing concentration, while the amount 

 of growth or, where present, the destruction of cellulose is indicated as 

 — = lacking, — h = very faint, + = distinct, ++ = fairly strong, and 

 -f-+-l- = vigorous. 



