β Scribed by McGuigan, H.A.
No coin nor oath required. For personal study only.
How shall we evaluate an unknown anesthetic in terms of cocaine? This necessitates a resume of the biological methods of determining the value of an anesthetic. Before such methods are applicable the drug must be known to be available as a local anesthetic, i. e., it must be devoid of certain properties: it must be non-corrosive and relatively non-toxic. Phenol, ammonia, and many other drugs, when injected hypodermically, produce anesthesia; but the preliminary pain and corrosive action is sufficient to eliminate them from consideration. Such drugs have been called anesthetica dolorosa.
The methods used by pharmacologists to determine the value of local anesthetics are:
I. The anesthetization of the conjunctiva of the rabbit's eye. This is car- ried out by dropping a solution of the drug into the conjunctival sac and determinitig the time of onset, and the duration of the anesthesia produced. The condition of anesthesia is determined by touching the cornea with a bristle or other sttitalde instrument. When anesthetized, no winking results, and no pain is elicited when the conjunctiva is irritated.
Anesthetization by dipping the foot of a frog into a solution of thf anesthetic, and determining when i t is anesthetized by dipping it in an acid solution. When anesthesia is induced the foot is not withdrawn from the acid solution. If it is withdrawn, the acid is washed off by dipping the foot in water and again immersing in the anesthetic solution until anesthesia is produced. Such a condition is detcrmined by the absence of reflex when again immersed in acid. The wellknown Tiirck method is used in this procedure.
Anesthesia is also determined by applying the drug to the sciatic ncrve of a frog, and noting when the impulse or after-stimulation fails to elicit a contraction of the muscle. This is a motor nerve, but its use in the study of anesthesia is sanctioned by the accepted physiological law that every nerve impulse is similar to every other nerve impulse. The motor impulse is harder to block than the sensory, but in comparati1.e work when the same nerve is used, this makes no difference.
The quaddel or wheal method by injection intradermally in the skin of man, stimulating the area with a pin, hot iron or the like, and noting when the sensation disappears and returns.
He shaves an area of the skin about one inch square, and injects one cubic centimeter of a solution of the drug into this area, and determines the minimum weight of the drug which is necessary to be dissolved in 1 cc. to cause anesthesia in five minutes. \irith procaine he found this method sufficiently delicate to detect differences of seven per cent. of the required amount, which was 0.Oi gram per ce.
Another method which has been used by Drs. Burnett and Jenkins, worliirig under Dr. Adams a t the University of Illinois, is the Cold Fish Method. 'l'hey find that by putting gold fish into a solution of an anesthetic, they turn over when anesthetized in a manner resembling death. However, since they rapidly * Read before the Unofficial Conference of U. S. P. and N. F. Revision workers at Chicago, 11. 111, IV.
'. A modification of this has been used on dogs by Pittenger.
π SIMILAR VOLUMES