This ailment has so many causes that a complete description of them would fill a volume; but they may be briefly described by saying: that headaches are caused by poisonous substances in the blood, and by some disturbance in circulation and diseases of the nervous system.

The blood may contain toxic substances from indigestion, effete matter from incomplete elimination, or from the various micro-organisms that produce contagious or infectious diseases.

The periodical attacks of sick-headache are usually due to excess of uric acid in the system. The only cure known is to live mainly on a cereal diet, take out-door exercise, plenty of water and daily baths.

Disturbance in circulation results from disease, mental excitement and pressure from clothing. Headaches so produced can only be cured by removing the causes that produce them.

See diseases of the stomach, intestines, liver, asthma, rheumatism and epilepsy.