[HARRISON & KENNEDY] DISCOLOURATION OF CODFISH 129 



perature, but both tubes of 16 per cent, salt codfish broth with filter 

 paper half in and half out had abundant growth. As other experi- 

 ments had shown that 42° C. gave good growth, the results on the 

 agar slope can be explained only by the effect of light and that the 

 fibres of the paper evidently sheltered the organism and permitted 

 growth. • 



Thermal Death Point, Moist Heat. — The red surface growth on 

 agar slopes was scraped off and put into 16 per cent, salt, making a 

 very heavy suspension, pink in colour and very turbid. Three cubic 

 centimetres of this suspension were pipetted into small bulbs, which 

 were then hermetically sealed. The bulbs were immersed in a large 

 water bath for ten minutes at various temperatures. On removal 

 from the bath, the neck of the bulb was broken with sterile forceps 

 and the contents pipetted out and transferred to sloped 16 per cent, 

 salt codfish agar, to cured fish slants, to fresh codfish slants, and to 

 16 per cent, codfish broth with filter paper, with the following results: 



50° C. for 10 minutes — growth in 13 days in all tubes. 



il II < 1 1 < i I it < ( 



II II II <( <l <l II 



II II Q II II (< II 



II II II II II II II 



— no growth in 30 days. 

 This experiment was repeated three times with the same results. 



Effect of Dry Heat. — Solar salt was inoculated with a suspension 

 of the red organism in 16 per cent, salt solution, and then dried for 

 seventeen hours immediately afterwards. Crystals of this salt were 

 transferred to codfish agar and to codfish broth, containing 16 per 

 cent., 25 per cent, and 35 per cent. salt. The salt was then heated 

 in a drying oven at 97° C, and crystals were transferred to codfish 

 agar and codfish broth, of various salt contents, at the end of ten, 

 twenty, thirty, forty, fifty and sixty minutes. After incubation at 

 37° C. for eleven days there was no red colour in any of the tubes 

 except those made for control before the salt was heated. 



Chromo genesis. — The colour showed best on media containing fish 

 with high percentages of salt. The naturally occurring infection is 

 pink to rose red; the pink on the split surface and the red on the folds 

 of the skin. On salt fish agars and on paper partly immersed in salt 

 fish broth the usual colour is red, the former more translucent. The 

 colours most nearly approach La France pink (Ridgway) and the 

 deeper colours scarlet red to carmine (Ridgway). 



9— E 



