154 Messrs. H. G. Thornton and G. Smith. 



to have a much feebler effect in stimulating growth than an infusion which 

 had been kept for some weeks and in which bacteria had been allowed to 

 multiply before it was sterilised. 



On the other hand, the same infusion, after being left for several months, 

 lost much of its previous efficacy. Similar results were obtained with other 

 vegetable infusions. 



A typical experiment, showing the effect of the various dilutions of Miquel 

 solution, and of the presence and absence of organic matter in the medium, 

 may be seen in Table I. 



Table I. — Cultures inoculated on April 21. 



Tube 

 No. 



Composition of Medium. 



Growth on 

 April 29. 



Growth on 

 May 2L. 



:<-■£, 









None 



None 



2 



8 c.c. 



„ „ + 2 c.c. distilled H 2 











3 



6 c.c. 



„ „ + 4 c.c. „ „ 







>> 





4 



4 c.c. 



,, „ +6 c.c. „ „ 











5 



2 c.c. 



„ „ +8 c.c. „ „ 











6 



10 c.c. 







r 







7 



8 c.c. 



» j. + 2 c -°- ,, „ 



:: j & § 







8 



6 c.c. 



, ,, +4 c.c. „ ,, 



•• yfB 



\ 







9 



4 c.c. 



,, „ + 6 c.c. ,, ,, 



1 w <4-i 

 ■• 1 H fl 



i 



I 



Slight growth 





10 



2 c.c. 



„ „ + 8 c.c. „ ,, 



■J + 







11 



8 c.c. 



„ ., +2 c.c. tap water 



None 





12 



6 c.c. 



, „ + 4 c.'c. „ 







» 





13 



4 c.c. 



, „ 4 6 c.c. „ 







Slight growth 





14 



2 c.c. 



, „ +8 c.c. „ 







>> 





15 



8 c.c. 



,, +2 c.c. „ 



••""I 5* 



r 

 i 



None 





16 



6 c.c. 



, „ +4 c.c. „ 



"1*1 



Slight growth 





17 



4 c.c. 



, „ + 6 c.c. „ 



f o 3 



\ 



Very strong 



Very strong 









1 1-1 p 



i 



growth 



growth 



18 



2 c.c. 



, „ +8 c.c. „ 



■J + <S 



L 



Strong growth 



Good growth 



These experiments show that the best growth was obtained in tube No. 17, 

 in which the culture medium consisted of 4 c.c. Miquel solution + c.c. 

 tap water, to which 1 c.c. hay infusion was added ; while in those tubes to 

 which no organic matter was added, growth was either totally absent, or 

 else a slight growth was observed in those tubes in which the proportions 

 of Miquel and tap water approached the optimum. 



It must be noted that when tap water is replaced by distilled water, the 

 growth is either prevented altogether or else is very slight, even when the 

 necessary elements for growth are given in the Miquel and organic matter. 

 This can be seen in Table I in tubes Nos. 7-10, as compared with tubes 

 Nos. 15-18. A similar result was noticed when cultures were made with 

 Miquel fluid that had been made up with distilled water instead of tap 

 water. The improved growth in tap water might be due either to the 



