The _toxicity_ of novocaine is one-fifth or one-seventh of that of cocaine. When used in conjunction with adrenalin, its anæsthetic activity is equal to that of cocaine. When injected into the tissues it produces no irritant effects like certain other local anæsthetics, notably stovaine. For the production of local anæsthesia it is used in ½ per cent. solution with the addition of three or four minims of 1 in 1000 solution of adrenalin chloride to each ounce. Several ounces of this preparation may be used with the greatest safety. Allen makes the following statement regarding this drug:--“After a rather extended experience, including a large number of cases embracing the entire field of surgery, in which this agent has been almost exclusively used, we have failed to note a single case in which there has been any unpleasant local or constitutional action. We, therefore, feel thoroughly justified in unqualifiedly recommending it as the safest, most reliable, and satisfactory of any local anæsthetic agent yet introduced.” Tropacocaine. This drug was first isolated from the leaves of the coca plant of Java, but is now prepared synthetically. Its formula is C_{15}H_{19}NO_{2}. Its action is exactly the same as that of cocaine, except that it is one-half as toxic and the duration of anæsthesia is shorter. The hydrochloride is freely soluble in water, and can be boiled without fear of decomposition. It is the agent which is most suitable for spinal anæsthesia, as fewer unpleasant effects have followed its use than that of any other drug. Stovaine. Stovaine is the hydrochloride of a synthetic compound of the benzoyl group. It occurs as a white crystalline powder, soluble in water, 1 in 14. Its solutions withstand boiling, but are decomposed when heated to 120°C. Its action is the same as that of cocaine, except that it is slightly less toxic and less powerful. It has a distinct irritant effect locally. When injected in dilute solution, it produces a slight burning pain before anæsthesia appears, and very often a distinct inflammatory reaction persists for some time after the operation. It is therefore unsuited for local anæsthesia. It has been widely used for the production of spinal anæsthesia, especially by the French school, but since its injurious effects on nerve tissues have become more apparent, it has been less used than formerly. Eucaine. Eucaine was introduced as a substitute for cocaine, and, before the introduction of novocaine, was extensively used. It has a similar action to cocaine, and although it is less toxic, it is by no means free from danger unless it is used in very dilute solutions. It is a vaso-dilator, and must therefore be used in combination with adrenalin. It can be boiled without undergoing decomposition, and is practically non-irritant. It has been largely superseded by novocaine.