728 PRINCIPLES OF GENERAL PHYSIOLOGY 



above (page .344). Another useful property of atropine is to paralyse the vagus 

 endings in the heart, and also that of paralysing the mechanism of accommodation 

 in the eye, and causing dilatation of the pupil. Certain peculiarities in the mode 

 of action of pilocarpine have been mentioned above (page 143). 



lli/oscine. This alkaloid, allied to atropine, is of interest in connection with 

 the different activities of the natural alkaloids and their optical isomers. The 

 latter, although not inactive, are less so than the former. Now hyoscine contains 

 two optically active groups, both of which are physiologically active, so that four 

 different isomers exist, each with a different degree of activity. Cushny finds 

 that by assigning to each of the four constituents a definite value, that of each of 

 the four hyoscines can be deduced. The values differ less than those of the two 

 adrenalines. The question has some theoretical interest in connection with the 

 doctrine of fitting to templates or " lock and key." If this were the correct point 

 of view, it would be expected that only one of the isomers would be active, whereas 

 they only differ in degree. 



Veratrine. The peculiar effect of this alkaloid in producing tonic contraction 

 of skeletal muscle has been mentioned above (page 417). Lamm (1911) has 

 described some interesting experiments which throw light on its mode of action. 

 The conclusions which he draws are as follows. When a muscle is immersed in a 

 solution of a salt of veratrine, it takes up small amounts of the poison, probably 

 as free alkaloid, since the effect is more powerful in alkaline solution. A solution 

 can be exhausted by means of a series of muscles. The drug has no effect until 

 the muscle is stimulated independently. If the toxic action is small, the veratrine 

 " tetanus " does not come on until the initial twitch is over. There is no reason 

 to suppose that the kind of fibrillation taking place is due to stimulation of any 

 different kind of substance (sarcoplasm) than that responsible for the twitch. 

 It appears to be due to some kind of reaction between the poison and some 

 product of metabolism of the active muscle. Thus a solution which has served 

 for action on one muscle is found to be increased in activity. If a muscle is 

 disintegrated in a veratrine solution, it is found that apparently more alkaloid can 

 be extracted from the mass than was originally present in the solution. It is 

 suggested that the exciting action depends on an increase in permeability of the 

 cell membrane, since calcium salts markedly increase the amount necessary for an 

 effect. 



Ergotoxine. Dale (1906) and Barger and Dale (1907) have obtained from 

 ergot a preparation which has interesting properties. It paralyses those sym- 

 pathetic endings which have an excitatory function, leaving intact those with 

 an inhibitory function. Both kinds of fibres in the cranial and sacral autonomic 

 nerves are left untouched. Thus the vaso-constrictors of the sympathetic are 

 paralysed, but the inhibitory effect of the splanchnics on the small intestine is not 

 affected. Adrenaline, after ergotoxine, causes a fall of blood pressure, but it is 

 not quite certain whether this is actually due to a stimulation of sympathetic 

 vaso-dilators, or to constrictor endings whose function has been reversed by the 

 ergotoxine. 



Cushny 's book (1910, 2), will be found to contain any further information 

 required by the reader regarding the action of drugs. 



TOXINS AND ANTITOXINS 



Toxins are the poisonous substances produced by micro-organisms. They may 

 pass out into the culture fluid or be retained in the bodies of the microbes, only 

 to be obtained from these by disintegration. Their chemical nature is unknown, 

 since they can only be obtained in such small quantities. They are the substances 

 responsible for the numerous diseases produced by the agency of micro-organisms. 

 Pasteur showed, for example, that a culture of the bacterium of chicken cholera 

 produced the symptoms of the disease, even after filtering off the organisms 

 themselves. For further details, the reader is referred to the book by Burnet 

 (1911). 



Along with certain other substances, all of protein nature, so far as reliable 



