(2) If in ether anesthesia the blood vessels leading to and from the adrenal glands are first carefully tied, and then the glands are removed, excitement four or five hours later, before the weakness that follows the removal has become prominent, does not alter the blood so that the typical inhibition occurs (see Fig. 6). Thus, although the animal shows all the characteristic signs of sympathetic stimulation, the blood, in the absence of the adrenals, remains unchanged. [Illustration: Figure 6.--Failure of the cava blood (added at _a_) to produce inhibition when excitement has occurred after removal of the adrenal glands. The muscle later proved sensitive to adrenin in blood in the ratio 1:1,000,000.] (3) As already shown, sometimes the effect produced by the “excited” blood was prompt inhibition, sometimes the inhibition followed only after several beats, and sometimes a slowing and shortening of contractions, with a lower tone, were the sole signs of the action of adrenin. All these degrees of relaxation can be duplicated by adding to inactive blood varying amounts of adrenin. Fig. 7 shows the effects, on a somewhat insensitive muscle preparation, of adding adrenin, 1:1,000,000 (A), 1:2,000,000 (B), and 1:3,000,000 (C), to different samples of blood previously without inhibitory influence. These effects of adrenin and the effects produced by blood taken near the opening of the adrenal veins are strikingly analogous. [Illustration: Figure 7.--Effect of adding adrenin 1:1,000,000 (A), 1:2,000,000 (B), and 1:3,000,000 (C), to formerly inactive blood. In each case _a_ marks the moment when the quiet blood was removed, and _b_, the time when the blood with adrenin was added.] (4) Embden and v. Furth[43] have reported that 0.1 gram of suprarenin chloride disappears almost completely in two hours if added to 200 cubic centimeters of defibrinated beef blood, and the mixture constantly aerated at body temperature. “Excited” blood which produces inhibition loses that power on standing in the cold for twenty-four hours, or on being kept warm and agitated with bubbling oxygen. This change is illustrated in Fig. 8; the power of the “excited” blood to inhibit the contractions of the intestinal muscle when record _A_ was written was destroyed after three hours of exposure to bubbling oxygen, as shown by record _B_. The destruction of adrenin and the disappearance of the effect which adrenin would produce are thus closely parallel. [Illustration: Figure 8.--The effect of bubbling oxygen through active blood. A, relaxation after active blood applied at _a_; B, failure of relaxation when the same blood, oxygenated three hours, was applied to a fresh strip at _b_.]