

CEREBRAL STIMULANTS bU 



CEREBRAL STIMULANTS. The functions of the brain gener- 

 ally are stimulated by a large group of agents, sometimes 

 termed brain stimulants or exhilarants, and exemplified 

 by caffeine, theobromine, cocaine, atropine, and oil of 

 turpentine. Of these, the first two especially affect the 

 psychical side, whilst the others are motor stimulants 

 primarily. Ammonia vapour, liquor, or carbonate, applied 

 to the nostrils, reflexly stimulates the heart, and then acting 

 upon the vaso-motor centres, also increases general blood 

 pressure, and the circulatory improvement stimulates the 

 brain. Other circulatory stimulants act similarly. Brisk 

 exercise has much the same stimulating effect on the 

 cerebral as on other arteries and capillaries. Mastication 

 and sucking in young animals have been shown by experi- 

 ment to increase circulation in the carotids and cerebral 

 arteries. Chewing tobacco, betel-nut, or, indeed, anything 

 else, smoking, sipping alcoholic stimulants, or even tea, 

 coffee, or cold water, have similar effects in dilating the 

 human cerebral arteries. Placing the head on a lower level 

 than the rest of the body favours brain circulation, and 

 hence wards off syncope. 



The functional activity of the brain is lowered by large 

 or repeated doses of alcohol, which, after apparent exhilara- 

 tion, and, it may be, delirium, produce narcosis, sleep, and 

 sometimes death. Other agents causing depression, after 

 more or less preliminary excitement, are chloroform and 

 chloral, opium and cannabis indica. Bromides of potassium 

 and ammonium, without preliminary excitement or dis- 

 turbed function, diminish brain activity. Accumulation of 

 lactic acid, and probably other elements of tissue waste, 

 appears to have an effect similar to that of the bromides in 

 lowering the activity of the nerve-cells. 



SOPORIFICS or HYPNOTICS are agents which induce sleep. 

 Many hypnotics lessen functional activity of the nerve-cells 

 of the brain and spinal cord, while others impede the im- 

 pressions transmitted through the nerves and special sense 

 organs to the cerebrum. Full doses further depress the 

 functions of the respiratory and vaso-motor centres in the 

 medulla, as evidenced by slower respiration, dilatation of 

 surf ace- vessels, and lowering of arterial tension. During 



