66 MEDICINES ACTING ON THE NERVOUS SYSTEM 



is shown by the fact that the arterioles in the lungs, which 

 are practically without vaso-motor nerves, are constricted 

 when a solution of barium chloride is perfused through them. 

 The opposite effect, namely, direct relaxation of unstriped 

 muscle fibres, is brought about by nitrites, such as amyl- 

 nitrite, and with these the lung vessels become widely dilated. 



MEDICINES ACTING ON THE NERVOUS SYSTEM 



ON THE BRAIN. CEREBRAL STIMULANTS EXHILARANTS 

 CEREBRAL DEPRESSANTS SOPORIFICS NARCOTICS - 

 ANODYNES ANTISPASMODICS ANAESTHETICS. 



ON THE SPINAL CORD. SPINAL STIMULANTS AND DEPRESSANTS. 



ON MOTOR NERVES. STIMULANTS PARALYSERS. 



ON SENSORY NERVES. STIMULANTS LOCAL SEDATIVES- 

 LOCAL ANAESTHETICS. 



ELECTRICITY. 



The nervous system of the higher animals comprises : 

 I. The brain, which takes cognisance of external im- 

 pressions, co-ordinates movements, and originates 

 mental or psychical ideas. Relatively to other 

 parts of the nervous system, the brain of man 

 is more highly developed than that of animals, 

 and most drugs, accordingly, act upon it more 

 powerfully than upon the less developed brain of 

 the horse, ox, or dog. The brain consists of (1) the 

 medulla, pons, iter, corpora quadrigemina and 

 third ventricle, which may be looked upon as con- 

 tinuing the spinal cord forward and giving off 

 cranial in place of spinal nerves ; (2) the cere- 

 bellum, which is chiefly concerned in the mainten- 

 ance of equilibrium ; and (3) the cerebral hemi- 

 spheres. The cerebral hemispheres are concerned 

 with the highest functions of judgment and will 

 power, and are the seat of the intelligence. This 

 is especially the part of the brain which is most 

 highly developed in man. The cerebrum controls 

 and co-ordinates movement, and in the grey 

 matter of the cerebral cortex are the motor cells 

 from which these impulses spring. 



