210 INTERNAL SECRETION 



million ; in other words, the dilation of the pupil demonstrates the 

 presence of adrenalin 'in a quantity as small as .000025 m g- 

 This mydriasis of frogs' eyes was subsequently employed as a 

 test for adrenalin in liquids of the most varied description (blood, 

 urine), but the results were not in all cases unequivocal ; that is 

 to say, they were not characteristic of adrenalin only. 



It has since been discovered that, in addition to adrenalin, 

 a large number of substances provoke dilation of the pupil of 

 isolated frogs' eyes. Waterman and Boddaert produced this 

 effect with weak watery solutions of pyrocatechin, with salicylic 

 acid, hydrokinone, and resorcin ; they think the reaction is 

 dependent upon pyrocatechin. Ehrmann found that acetic acid 

 and ammonia produce irregular dilation of the pupil, but that 

 the pupil also contracts in response to these reagents. According 

 to Pick and Pineles, tyrosin and phenylalanin produce mydriasis 

 of the frog's eye ; Cramer, Borchardt and Pal attribute the same 

 effect to pituitary extract; Ranzi and Tandler to thymus extract. 

 Pick and Glaessner obtained a mydriatic reaction with the pan- 

 creatic juice of man and of dogs, which was particularly marked 

 where these subjects had been previously fed upon meat. 

 According to Comessati and Diem, the mydriasis of frogs' eyes, 

 when employed as a test for the presence of adrenalin in urine 

 or in concentrated saline solutions, has very little value. 



We shall have occasion to speak later of the mydriatic action 

 of the blood serum, and of the theories which have arisen concern- 

 ing the presence of adrenalin in the plasma under both normal and 

 pathological conditions. For the present, it is sufficient for us 

 to notice the fact that the mydriasis of frogs' eyes is, in itself, 

 not a conclusive proof of the presence of adrenalin in the blood 

 serum ; this test should always be reinforced by other biological 

 and chemical reagents. 



The action of adrenalin has also been put to practical use 

 in another direction. Lewandowsky was the first to discover 

 that the instillation of suprarenal extract into the conjunctiva is, 

 in the case of both man and animals, without effect upon the 

 pupil. Melzer and Auer next showed that, after extirpation of 

 the superior cervical ganglion of both rabbits and cats, the 

 instillation of adrenalin produces a considerable enlargement of 

 the pupil. We know that the sympathetic contains fibres which 

 promote contraction of the dilator muscles of the pupils. If, 

 therefore, stimuli which are inactive or only slightly active in 

 the case of normal eyes, react strongly upon eyes which have 

 lost their ganglion, we must assume the presence of sympathetic 

 inhibitory fibres which take their rise in the ganglion and by 

 which the peripheral irritability is reduced. O. Lowi assumed 

 that the occurrence or non-occurrence of mydriasis after adrenalin 

 instillation, was an expression of the functional activity of the 

 sympathetic inhibitory nerves. He therefore endeavoured to find 



