This book deals with the habit of eating clay, plaster, charcoal, or other unusual things. The author's hypothesis is "that poor nutrition may be the underlying factor in pica," and she tries to document her point by a historical review reaching back many centuries, from reports of colonial physicians on the habits of plantation workers and from earlier European and American authors.
The behavior of domestic animals and the self-regulatory functions as observed in studies of laboratory animals and young children as well as some (although meager) recent studies also support her thesis. A study conducted in Baltimore in which the author participated also indicates that pica is related to nutritional factors (feeding problems) and illness and physical defects but not to intelligence, other behavior problems, birth weight, age of weaning, or family income.
An analysis of edible earths indicates that they may contribute to nutrition by the effect of