The appetite may be depraved to an almost unlimited extent, as exemplified in the dietetic habits of the various peoples of the earth. Pica is a form of perverted appetite which manifests itself in the eating of chalk, clay, sand, coal, charcoal, hair, paint, cloth, dirt, acids, cinders, ordure, fire, bits of wood, candles, paper, leaden-bullets, glass, beads, stone, knives, marbles, pieces of money and various other indigestible and non-nutritious substances. Akin to this is the eating of spiders, lice, toads, serpents, leeches, snails, etc. No doubt the eating of salt, pepper and other condiments and the use of tobacco, betel, or other such substance, should also be classed as perversions of the sense of taste.

The depraved appetite is sometimes the result of deliberate cultivation as in the use of salt, condiments and tobacco. It is sometimes a symptoms of "disease." In hysteria, chlorosis, pregnancy and certain mental and nervous ailments, the appetite often craves the most singular and disgusting articles.

Disturbed or inadequate nutrition may be at the base of much of this perversion. A lack of minerals or vitamins may give rise to a vague, ill-defined craving that causes the victim to eat anything in an effort to satisfy his craving. In pregnancy and chlorosis the abnormal cravings seem certainly to be due to nutritive deficiencies and soon yield to proper feeding. Frequent sun bathing of children is claimed to aid in preventing abnormalities of taste in them.

Dirt eating or African Cachexia, is a form of depraved appetite (pica) that prevails among the negro population of hot climates and appears to belong to the negro race almost exclusively. The individual so depraved experiences an irresistible craving for substances of an indigestible and disgusting character. Clay, earth, mortar, dust, ashes, chalk, slate, bricks, and shells are often devoured in enormous quantities, while food is almost wholly rejected as disgusting and worthless. The appetite seems to be wholly depraved. The condition has long been known in tropical America and has been observed in the southern part of the United States.

Of a similar character to filth eating is that perversion of the sense of taste that manifests itself in salt-eating, condiment using, tobacco chewing, snuffing and smoking, pickle eating, drinking of alcoholic and soft drinks, and the use of other such substances. None of these things supply any need in the human body. None of them are essential to normal enjoyment of food. All of them are harmful. A taste for them must be cultivated before they can be enjoyed, after which they enslave their victims as truly as the coffee habit, tea drinking or morphine using.

What Jennings called a "good physical conscience" is the sum total of an individual's unimpaired, unperverted instincts and reflexes. It may be well to impress the reader with the importance of maintaining a clear "physical conscience." The advantages of a good physical conscience are too obvious and too numerous to need or admit of a full notice here. The individual who is so fortunate as to possess one, is in much less danger of violating physical law than one who does not. If the former were to receive into his stomach hut a small particle of black pepper, though ultimately mixed with his food, unperceived by him at the time,'it would inflict a pang on the tender, upright sensibility, that would be remembered a long time, and operate as a caution against further transgression. Another benefit derived from a good physical conscience, is that while it guards against the admission of noxious substances into the system, it also imparts a very high relish to those plain, simple substances, that are adapted to the wants of the body."