472 TRANSACTIONS OF SECTION I. 



the most specific reagents for certain forms of living matter which we possess. 

 Thus, if ail organ reacts to aiJrenalin, we can infer that it contains the sub- 

 stance characteristic of the terminations of sympathetic fibres, witli ahiiost as 

 great certainty as we infer the presence of a phenol group from the reaction 

 with iron. And this sympathetic substance can be further analysed into two 

 parts by means of ergotoxine, which reacts with the substance of the motor 

 sympathetic ends, while leaving that of the inhibitory terminations unaffected. 

 Similarly the endings of the parasympathetic nerves are picked out with some 

 exceptions by the groups represented by atropine and pilocarpine, and here 

 again there must be some definite substance which can be detected by these 

 i-eagents. 



FurtTiei*, some light has been thrown on, at any rate, one aspect of these 

 nerve-end substances by the observation that they all react to only one optical 

 isomer in each case. Thus the dextro-rotatory forms are ineffective in both 

 atropine and adrenalin, and this suggests strongly that the reacting body in 

 the nerve-ends affected by these is itself optically active, though whether it bears 

 the same sign as the alkaloid is unknown. This Very definite differentiation 

 between two optical isomers is not characteristic of all forms of living matter. 

 For example, the heart muscle seems to react equally to both Isevo- and dextro- 

 camphor. The central nervous system contains substances which react some- 

 what differently to the isomers of camphor and also of atropine, but the 

 contrast is not drawn so sharply as that in the peripheral nerve-ends. 



Another test alkaloid is curarine, the active principle of curare, which in 

 certain concentrations selects the terminations of the motor nerves in striated 

 muscle as definitely as any chemical test applied to determine the presence 

 or ab.sence of a metal. 



The tyro in the chemical laboratory is not often fortunate enough to be 

 able to determine his analysis with a single test. He finds, for example, 

 that the addition of ammonium sulphide precipitates a considerable group of 

 metals, which have then to be distinguished by a series of secondary reactions. 

 Tlie pharmacologist, as an explorer in the analysis of living matter, also finds 

 that a single poison may affect a number of structures which appear to have 

 no anatomical or physiological character in common. But as the chemist 

 recognises that the group of metals which react in the same way to his reagent 

 have other points of resemblance, so perhaps we are justified in considering 

 that the effects of our poison on apparently different organs indicate the 

 ■presence of some sub.stance or of related substances in them. A great number 

 of instances of this kind could be given, and in many of these the similarity 

 in reaction extends over a number of poisons, which strengthens the view that 

 the different organs involved have some common reacting substance. 



One of the most interesting of these is the common reaction of the ends 

 of the motor nerves in striated muscle and of the peripheral ganglia of the 

 autonomic system. It has long been known that curare and its allies act 

 in small quantities on the terminations of the motor nerves in ordinary muscle, 

 while larger amounts paralyse conduction through the autonomic ganglia. More 

 recently it has been developed by the researches of Langley that nicotine and 

 its allies, acting in small quantities on the ganglia, extend their activities to 

 the motor-ends in large doses. Some drugs occupy intermediate positions 

 between nicotine and curare, so that it becomes difficult to assign them to 

 either group. These observations appear to leave no question that there is 

 some substance or aggregate common to the nerve-ends in striated muscle and 

 to the autonomic ganglia. As to the exact anatomical position of this sub- 

 stance, there is still some difference of opinion. Formerly it was localised in 

 the terminations of the nervous fibre,s in the muscle and ganglia, but Langley 

 has shown that in the latter the point of action lies in the ganglion-cell itself, 

 and his researches on the antagonism of nicotine and curare in muscle appear 

 to show that the reacting substance lies more peripherally than was supposed, 

 perhaps midway lietween the anatomical termination of the nerve and the 

 actual contractile substance. Another analogy in reaction has been shown to 

 exist between the ganglia and the terminations of the post-gangl ionic fibres of 

 the parasympathetic, for Marshall and Dale have pointed out that a series of 

 substances, such as tetramethyl-ammonium, affect each of these in varying 

 degrees of intensity. The specific character of the reaction is shown by the 



