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The manufacture of butadiene from ethanol by the American two-step process developed by Car-bide and Carbon Chemicals Corporation3•4 and operated by that organization and by Koppers Company, Inc., comprised (1) dehydrogenation of ethanol to acetaldehyde followed by (2) catalysis of acetaldehyde-ethanol to produce butadiene. This paper discusses the mechanism of the second step, ih which a mixture of approximately 69 wt. % of ethanol, 24 wt. % of acetaldehyde and 7 wt. % of water was passed over a 2% Ta20s-98% SiOj cata-

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SUMMARYThe ability of various compounds to support swarming of Proteus was determined by making additions to a minimal medium agar on which swarming did not occur. Swarming occurred when alanine, asparagine aspartic acid, glutamic acid, glutamine, proline or serine were present, either individually or together. It did not occur when certain other amino acids were added individually to minimal medium agar but did occur when these were added together. The ability of a compound to support swarming was correlated with its ability to serve as a carbon +energy source and with the stimulation of growth rate. The swarming phenomenon is discussed in the light of these findings. I N T R O D U C T I O NMany members of the bacterial genus Proteus exhibit the phenomenon of swarming when grown on solid medium (Plate 1). When inoculated at the centre of a plate of suitable medium and incubated aerobically at 30-37" the culture grows as short organisms for a few hours; then organisms at the edge of the colony thus formed elongate and spread over the surface, i.e. they swarm. Movement stops after 1-2 hr. Division of organisms at the edge of the colony then occurs, to give short organisms, and the cycle is repeated. All organisms beyond the edge of the initial colony constitute the swarm. The swarming phenomenon of Proteus has been described by many workers, with slight variations in their descriptions (

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