XXXIX NO . 9 PREPARATION OF l-ACYLOXYETHYL FSTERS OF 7 [ 2-( 2-AMINOTHIAZOL-4-YL ) ACETAMIDO } 3-[ [ [ 1-( 2-DIMETHYLAMINOETHYL )-1 H-TETRAZOL 5-YL ] THIO ]-METHYL ] CEPH-3-EM-4-CARBOXYLIC ACID ( CEFOTIAM ) AND THEIR ORAL ABSORPTION IN MICE