We studied two methods to reduce the ordering of laboratory and radiologic tests by medical residents in their first postgraduate year. Dividing the residents into three groups, we compared the effect of concurrent chart review and discussion in one group with the effect of a moderate financial incentive for limited ordering of tests in a second group. The third group of residents served as a concurrent control, and data on the testing patterns of residents at the same hospital during the year before the study provided a retrospective control.

An investigation has been made of the mode of attack of cellulose by periodic acid during the early stages of the oxidation (that is, oxidation of approximately 1 percent of tb~ glucose residues). Under these conditions, it is shown that the reaction is confined to oxidation of the secondary hydroxyl groups to aldehyde groups, and results in a rupture in the carbon chain between carbon atoms 2 and 3 of the glucose unit. In accordance with this mechanism it is shown that two moles of aldehyde groups are produced for each mole of oxidant consumed. The aldehyde groups of the periodic acid-oxycellulose can readily be converted to carboxyl groups, titration of which provides an independent check on the content of the former.Periodic acid-oxycellulose is characterized by its susceptibility to further attack by alkaline solutions. The a lkali-sensitivity of these materials, as measured by solubility in hot dilute sodium hydroxide and by cuprammonium fluidity, appears to be proportional to the content of aldehyde groups. However, upon conversion of all of the a ldehyde groups to carboxyl groups, the alkali-lability practically disappears. The results suggest that the sensitivity of periodic acid-oxycellulose to alkali does not depend solely on the rupture of the glucose ring between carbon atoms 2 and 3, but is related to the specific instability towards alkali of the dialdehyde formed during the oxidation. CONTENTS Page

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