On fundamental changes in the action of some alkaloids upon frogs after cardiectomy or ligation of one aorta

At the last meeting of the American Physiological Society I reported that in cardiectomized frogs an injection of adrenalin will still cause dilatation of the pupil and an injection of strychnine will cause a tetanus. At the February meeting of this society I reported on the action of morphin on cardiectomized frogs. An injection of 10 or 15 mgr. of morphin in living, normal, medium-sized frogs causes at first no perceptible effect; after a few days a tetanus may set in, while there is at no time a depression. In cardiectomized frogs, however, an injection of 6 or 8 mgr. of morphin causes the appearance of tetanic symptoms in less than an hour. When 10 to 20 mgr. are injected the tetanus is preceded by a paretic state. After an injection of 25 to 30 mgr. the animal becomes paralyzed very early, to be interrupted later by only short weak tetanic movements.

I have since found that also after the ligation of one aorta, especially of the right one, a tetanus will very frequently develop two or three hours after an injection of 10 or 15 mgr. of morphin; in some cases the tetanus may persist as long as twenty hours. In some cases two or three hours after the development of the spasmodic state the tetanus became temporarily interrupted by paralysis which lasted only 30 to 60 minutes.

Since the beginning of April it often became difficult to obtain in cardiectomized frogs a tetanus; even with small doses of morphin the effect was in many cases complete paralysis, which set in very early after the injection. The same was true also of frogs with one aorta ligated. Here the heart might be seen beating forcefully for hours while the animal is completely paralyzed.