HORMONES, DRUGS, AND TOXINS 713 



work of other observers will be found in the paper. Those of Cheboksarov (1910) 

 may be especially mentioned. 



Suppose, then, that a drug is given which stimulates the splanchnic nerves. 

 It is clear that the effects obtained will be combinations of those of the drug 

 itself with those of the adrenaline sent into the blood. Dale and Laidlaw 

 (1912, 2) have found that nicotine and pilocarpine produce effects of sympathetic 

 stimulation on the cat's uterus in situ, but not when excised. Also the effect of 

 nicotine in causing dilatation of the pupil, after the sympathetic supply had been 

 cut off, was found to be absent if the suprarenal bodies were excluded from the 

 circulation. The glycosuria produced by puncture of the floor of the fourth 

 ventricle is probably also due to secretion of adrenaline. 



Although, under experimental conditions, there seems to be no doubt that the 

 blood of the suprarenal vein contains more adrenaline than that of the artery, 

 some discussion has arisen as to whether the normal blood pressure is, under 

 normal conditions, maintained to any extent foy a constant inflow of adrenaline. 

 When the effect of the venous blood from the" suprarenal gland on the arteries of 

 the frog is compared with that of known concentrations of pure adrenaline, and 

 this again with the amount required to produce a permanent rise in the blood 

 pressure of the mammal, it appears that the amount sent into the blood by the 

 unstimulated suprarenals is too small to produce any perceptible result. Further, 

 Trendelenburg (1914) was unable to find any difference between the average blood 

 pressure in cats, unansesthetised and quiet, before and directly after removal of the 

 suprarenals. 



Adrenaline is, then, a hormone, used only for special purposes, and unlike 

 some of those to be mentioned presently, which are in constant activity. 



The Cortex of the Suprarenals. Elliott (1913, i. p. 316) points out the 

 remarkable fact, although it does not appear to have any physiological significance, 

 that so many ductless glands, the pituitary, suprarenals, thyroid, pancreas, testis, 

 etc., are of double nature. This renders analysis difficult. 



The cortex of the suprarenals has no particular relation to the sympathetic 

 nerves. The presence of a considerable amount of a lipoid substance appears 

 to be an indication of a healthy state of activity. It is supposed that the absence 

 of the cortex is associated with the bronzing of the skin in Addison's disease. 

 There is also evidence that overgrowth of the cortex in children is associated with 

 sexual precocity and premature adolescence. 



Carbon Dioxide. The distinction of this substance as a parahormone by Gley, 

 and the development of special sensibility on the part of the respiratory centre 

 to increase of hydrogen ion concentration in the blood, caused by its presence, 

 have been already referred to. The work of Hasselbalch and Lundsgaard (1911), 

 and of Hasselbalch (1912), may be added as containing the most accurate 

 determinations of the hydrogen ion concentration of the blood in connection 

 with stimulation of the respiratory centre. 



It seems very doubtful whether carbon dioxide has any particular function 

 as a hormone in any other respect. The "acapnia" of Mosso, as responsible 

 or mountain sickness, has been shown by Haldane and his co-workers not to 

 oe the correct explanation. Yandell Henderson has published a series of papers 

 in the American Journal of Physiology, from 1908 onwards, advocating the 

 importance of carbon dioxide as a necessary constituent of the blood, and 

 explaining various phenomena as being due to its too small concentration. In 

 so far as its removal reduces the optimal hydrogen-ion concentration for numerous 

 processes, this removal has, of course, an injurious effect. ^ The evidence that other 

 apparent effects cannot equally well be explained in other ways is not very strong. 



The Reproductive Organs. It has been known for centuries that removal 

 of the sexual glands produces profound changes in the organism. But it is 

 only comparatively recently that exact observations have been made on the 

 phenomena. 



Perhaps the most striking results to commence our brief study with are those 

 of Steinach (1910). If the testes are removed from frogs, the "clasp reflex" 

 is abolished. Of course, the nerve centres concerned remain, and it is not 



