Here, then, is a remarkable group of phenomena--a pair of glands stimulated to activity in times of strong excitement and by such nerve impulses as themselves produce at such times profound changes in the viscera; and a secretion given forth into the blood stream by these glands, which is capable of inducing by itself, or of augmenting, the nervous influences which induce the very changes in the viscera which accompany suffering and the major emotions. What may be the significance of these changes, occurring when conditions of pain and great excitement--experiences common to animals of most diverse types and probably known to their ancestors for ages past--lay hold of the bodily functions and determine the instinctive responses? Certain remarkable effects of injecting adrenin into the blood have for many years been more or less well recognized. For example, when injected it causes liberation of sugar from the liver into the blood stream. It relaxes the smooth muscle of the bronchioles. Some old experiments indicated that it acts as an antidote for muscular fatigue. It alters the distribution of the blood in the body, driving it from the abdominal viscera into the heart, lungs, central nervous system and limbs. And there was some evidence that it renders more rapid the coagulation of the blood. There may be other activities of adrenin not yet discovered--it may coöperate with the products of other glands of internal secretion. And other glands of internal secretion may be stimulated by sympathetic impulses. But we were not concerned with these possibilities. We wished to know whether the adrenin poured out in pain and emotional excitement produced or helped to produce the same effects that follow the injection of adrenin. Our later researches were concerned with answers to this question. REFERENCES [Footnote 43: Embden and v. Furth: Hofmeister’s Beiträge zur chemischen Physiologie und Pathologie, 1904, iv, p. 423.] [Footnote 44: Elliott: Journal of Physiology, 1905, xxxii, p. 448.] [Footnote 45: Elliott: Journal of Physiology, 1912, xliv, p. 409.] [Footnote 46: Hitchings, Sloan and Austin: Cleveland Medical Journal, 1913, xii, p. 686; see also Crile and Lower: Anoci-association, Philadelphia, 1914, p. 56.] CHAPTER V THE INCREASE OF BLOOD SUGAR IN PAIN AND GREAT EMOTION