BY R. GREIG SMITH. 573 



colour as it slowly gravitates. Gas bubbles are sometimes formed 

 in the medium. 



Nutrient gelatin stab. — A filiform white growth; the nail-head 

 has a raised margin and depressed centre; the medium is con- 

 sumed and slowly liquefies funicularly. 



Ghccose-gelatin stab. — The growth is as on nutrient gelatin but 

 stronger; the nail-head is at first uniformly raised, but becomes 

 corrugated and terraced. The filiform stab becomes coiled as the 

 neighbouring medium softens, but no liquefaction is apparent. 

 Gas bubbles form in the medium. 



Potato. — A pale bufi" or canary-coloured glistening, rough 

 growth is formed, while the medium darkens. 



Bouillon. — The medium becomes turbid, and a slight surface 

 film and coherent sediment is formed. Indol is produced, and 

 nitrates are reduced to. nitrites. 



Milk. — The medium is slowly and slightly thickened and it 

 then coagulates at 55''. 



(Plate XXXV.) 



