THE RELATIONS OF THERAPEUTICS 155 



true, and its power of slowing the pulse was known, but was not 

 utilized therapeutically. A proof of how little significance was 

 attached to these purely clinical experiments may be found in the 

 changes as to the admission of digitalis to the London Pharmacopeia. 

 In the year 1721 it was included; in 1746 rejected, and not reac- 

 cepted until 1778. 



Now in the year 1846, Weber made the surprising discovery that 

 the vagus nerve has an inhibitory influence upon the heart, i. e., 

 that exciting this nerve causes slower pulsation, and that cutting it 

 occasions extreme acceleration of the action of the heart. This 

 decisive experiment formed the basis of Traube's clinical investiga- 

 tions, and he was able to prove that the effect of digitalis on the 

 heart corresponded to the excitation or section of the vagus nerve. 

 This fact has been utilized clinically in diseases of the heart, arterio- 

 sclerosis, and dropsy, and now upon a firm basis, so that digi- 

 talis has emerged from its former position of uncertainty and taken 

 a place among the efficient and reliable remedies, and we can safely 

 say that it will not again disappear from the pharmacopeia, at any 

 rate not owing to any uncertainty as to its effect. 



Such investigations have now been undertaken with a number of 

 other preparations, and on a large scale, such as, for instance, the 

 clinical researches of Sir Lauder Brunton on"casca" (erythrophleum) 

 and of Sir J. T. Fraser on Strophanthus hispidus, a plant similar to 

 digitalis, but differing in its effect on the vaso-motor system, and 

 which was also soon adopted in therapeutics. Much the same may 

 be said of atropine, which chiefly through the knowledge of its phys- 

 iological effect on the iris, on the non-striated muscular system and 

 the glandular secretions, affords us an exact indication of its scope 

 of utility in disease. 



Thus we have here a source of fresh observations. Often the 

 functions of the organism are affected in an isolated manner that 

 we should scarcely have thought possible, for instance, by yohimbin. 



This physiological method is applicable to all chemical bodies, 

 and the progress in our knowledge of curative powers depends 

 solely on the progress of experimental physiology. 



The physiological action, however, does not always remain within 

 the limits of what is normal, for it may sometimes become patho- 

 logical. This was remarked by various scientists as early as the 

 middle of the eighteenth century, and shortly before the beginning 

 of the nineteenth century (1799) A. Fr. Hecker expressed this view 

 in his Physiologia Pathologica, i. e., in " the theory of the composi- 

 tion and functions of the human body and its different parts in 

 an abnormal condition." 



How differently we may view physiologically active bodies can 

 best be seen in the blood. But here, too, we observe that a rational 



