Ethel M. Doidge 421 



colonies were up to 5 mm. diameter and each sunken in a saucer of 

 liquefaction, the liquefied gelatine was clear and the colonies denser in 

 the centre than at the circumference. On the tenth day the gelatine in 

 the thinly sown plates was completely liquefied, the medium being very 

 slightly clouded. Colonies were still intact but somewhat diffused, up to 

 15 mm. diameter and often rolled at the edges; they were not tough, but 

 gelatinous in consistency, breaking very readily if an attempt were made 

 to lift them with a needle. Under the low power of the microscope the 

 centre was moruloid to grumose. 



Stab cultures in nutrient gelatine + 15. After 24 hours there were 

 slight indications of growth at the surface and along the upper part of 

 the stab, and on the third day there was a shallow crater of liquefaction 

 at the surface. On the fourth day liquefaction was crateriform, 7-10 mm. 

 wide and about 5 mm. deep; there was a good surface growth and a 

 slight bacterial deposit on the unliquefied gelatine, but the liquefied 

 part of the medium was colourless. Subsequently liquefaction became 

 stratiform, and when it had proceeded to a depth of about 1J cm. 

 growth apparently ceased. The gelatine remained clear or very slightly 

 cloudy, and eventually the surface growth sank to the bottom of the 

 liquefied portion. 



Streak cultures on nutrient gelatine + 15. A whitish streak about 

 1 mm. wide is visible after 24 hours, which is replaced on the second day 

 by a narrow channel of liquefaction along the needle track ; this channel 

 gradually becomes more extensive, the bacterial growth being carried 

 with the liquefied gelatine to the bottom of the tube. This continues 

 until there is 1-1-5 cm. of liquefied gelatine at the bottom of the 

 tube. 



Shake cultures in nutrient gelatine + 15. Numerous minute surface 

 colonies appeared in the third day, and the gelatine was slowly liquefied 

 from the surface downwards, liquefaction being first noticed on the 

 fourth day. At no time was there any growth in the depth of the 

 medium. 



Potato. On steamed potato cylinders a spreading, wet-shining 

 butyrous growth covered the moister parts of the cylinder in 24 to 

 48 hours; on the sloping surface there was a broad, more or less raised 

 streak surrounded by a narrow white "fermentation zone." The growth 

 was amber yellow, and became somewhat viscid, especially in old cul- 

 tures; it increased in quantity, covering the whole cylinder unless the 

 medium was dry; the colour deepened somewhat with age and the 

 medium was somewhat greyed. 



