The symptoms from both causes manifest themselves in exactly the same way, therefore it becomes very necessary to ascertain what the sufferer has been eating, both as to quantity and as to kind of foods during the previous forty-eight hours.
Colds caused by overeating
It often occurs that colds from overeating are cumulative, that is, the patient habitually takes too much fat, sweets, or meat, especially the two latter articles, and these may have been digested, and their nutritive elements may have passed into the circulation, but the body being unable to use them, they finally begin to decompose and are converted into alcohol and other decomposition products. An excess of this effete matter brought to the lungs is called a "cold."
If one who is blessed with good digestion and assimilation should habitually take an amount of nutrition in excess of his needs, it will manifest itself first, perhaps, in the growth of adipose tissue, and later in the various disorders called autointoxication, among which are colds, catarrh, etc.
Colds caused by exposure
If the body be exposed to a violent draft of cold air, and sufficient motion is not exerted to keep the circulation active, or if the feet be exposed to cold and wet, Nature, in obedience to the law of self-defense, closes the pores of the skin against the intrusion, hence the poisonous and effete matter that is constantly passing off through these openings cannot escape, but it is picked up by the blood and carried to the lungs to be oxidized or burned in the process of breathing.
Colds from overeating and exposure, identical
If the amount of poisons thus brought to the lungs be in excess of the amount that can be consumed or burned, a form of congestion will take place (in the lungs) causing first irritation, then suppuration, which must be thrown off in the form of mucus. It matters not whether the congestion is caused by exposure or overeating, the effects are identically the same, and Nature's method of ridding the body of these poisons is the same in either case. The only difference between an ordinary cold and pneumonia is one of degree.