Typing the gonococcus.

withdraw the dose into the same syringe." Three out of four manufacturers of insulin give almost identical instructions. Only A.B. Insulin Ltd. state: "Never change the type of insulin or the dose, or mix one type of insulin with another, except on the instructions of your doctor.. One well-known textbook' dealing with the subject of mixtures of soluble insulin and protamine zinc insulin states: "The two insulins can be given either as separate injections or mixed in the proper proportion immediately prior to injection." The Action and Uses Section B.P/B.P.C.2 after discussing the use of protamine zinc insulin goes on to state ". . . a dose of unmodified insulin is often given at the same time to tide over the period until the protamine zinc insulin is absorbed: the two insulins may be mixed in the syringe immediately before the injection is given." Malins, writing in Prescribers' Journal,3 discusses protamine zinc insulin and states: "P.Z.I. is still widely used though it contains an excess of protamine that will convert a proportion of any soluble insulin which may be added to it into the long acting form. Nevertheless, P.Z.I./S.I. mixtures have been surprisingly successful...." On the other hand, a standard textbook of therapeutics4 discussing the same subject states: .... some insulin preparations ... cannot be mixed with one another in the same syringe as this would alter their normal times of action-for example, soluble insulin and protamine zinc insulin." It is apparent that there is a difference of opinion regarding the mixing of soluble and protamine zinc insulin. In my view such mixtures introduce a degree of unpredictability in the time of action by reason of the variable combination of soluble insulin with the excess protamine present in protamine zinc insulin. Whatever our views, three out of four major manufacturers of insulin make no allowance for such differing opinions in the instructions which thev enclose with their insulin preparations. The purpose of this communication is to bring this to the notice of members of the profession who may be unaware at present of the manufacturers' directions, and to promote a more uniform point of view so that the risk of patients receiving conflicting advice may be minimized.-I am, etc., D. N. S. MALONE.