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The registration of gamma rays in a spark chamber has been simulated by Monte-Carlo-calculation technique. The spark chamber pictures of these gamma-ray events having a known energy and direction of incidence have been analysed for determinability of direction of incidence. The values obtained for angular resolution depending on energy are compared with values derived by other authors.

The synthesis and in vitro structure-activity relationship of 7-ureidoacetyl cephalosporins carrying various substituents in the 3-position, compounds that showed an enhanced broad spectrum of antibacterial activity, has been outlined. Contrary to most of the previous observations with diastereomeric isomers of cephalosporins, it has been found that the L-side chain isomers also are very potent antibiotics and are even more active inhibitors of certain fl-lactamase-producing Gram-negative bacteria than the corresponding o-side chain isomers. SQ 69,613,oct-2-ene-2-carboxylic acid, sodium salt, the most active compound tested, except for activity against staphylococci, was as active in vitro as cefamandole.

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band at 21 50cm-'). Apparently, the extent to which reaction proceeds by route B depends on the nature of R' and R Z ; by this route, the hydrogen sulfide adds first to the isocyanide group, yielding the thioformamide ( 3 ) which then undergoes ring closure to (4). Formation of the non-cyclizing ethyl 3,3diphenyIL2-(thioformylamino)acrylate ( 3 f ) from ( I f ) and hydrogen sulfide shows that formation of thioformamides cannot be disregarded.The 2-thiazoline-4-carboxylic esters (4) are formed also,