METABOLISM, NUTRITION AND DIETETICS 565 



dilatation of the pupil in the excised eyeball of the frog, first 

 introduced by Meltzer, and afterwards developed by Ehr- 

 mann. The increase in the tone and the acceleration and 

 strengthening of the rhythmical contractions of an isolated ring 

 of rabbit's uterus have also been employed as a clinical test even 

 for such minute amounts of adrenalin as can exist in the circu- 

 lating blood (Practical Exercises, Chap. XIV.). The alkaloid is 

 used in medicine in the form of a dilute solution of adrenalin 

 chloride, as a styptic, and for reducing congestion in accessible 

 parts. The intense local anaemia which it causes when given 

 subcutaneously or by the mouth is one reason, perhaps the most 

 important, for the slow absorption on which depends the absence 

 of its general effects, including that on the blood-pressure, when 

 it is administered in this way. The function of the capsules, or 

 rather of the so-called ' chromaffin ' cells, which constitute the 

 medulla and stain brown with chromic acid or chromates, is to 

 secrete this substance, which is probably of great physiological 

 importance for maintaining the tonicity of the muscular tissues 

 in general, and especially of the heart and arteries. Adrenalin 

 was entirely absent from the suprarenals of a person who 

 had died of Addison's disease. There is some evidence that 

 the active substance is really given off to the blood, and that 

 normal plasma contains adrenalin in sufficient amount to be 

 detected by that effect on the uterus which has just been men- 

 tioned. But statements which connect the increased blood- 

 pressure in such conditions as chronic nephritis with hypertrophy 

 of the chromaffin tissue, an increased adrenalin production, and 

 an increased adrenalin content of the blood, must be received 

 with caution. In a series of cases with high blood-pressure 

 Fraenkel found no distinct difference in this regard between 

 the pathological and normal sera. The so-called experimental 

 arterio-sclerosis produced by repeated injections of adrenalin 

 into the blood of rabbits throws little light upon the question, 

 for the vascular changes, in so far as they have not been con- 

 founded with similar lesions occurring spontaneously in a con- 

 siderable proportion of rabbits, differ from those observed in 

 pathological arterio-sclerosis (M. C. Hill). An artificial adrenalin 

 or suprarenin has been synthetically prepared. Chemically it is 

 identical with the natural adrenalin obtained from the suprarenal 

 glands, but while the natural adrenalin rotates the plane of 

 polarization to the left, the artificial substance is optically in- 

 active. This is because it consists of equal parts of laevo- 

 rotatory and dextro-rotatory adrenalin. The artificial adrenalin 

 has approximately half the effect of the natural on the blood- 

 pressure, from which it may be inferred that the dextro-rotatory 

 isomer has only a very slight pressor effect. Quite recently 



