Page:Popular Science Monthly Volume 46.djvu/399

Rh elbow. Here, again, according to Darwin, rain has been the modifying agent; the habit of clasping the hands over the head during rain has caused the rain to flow from the hands to the elbows, and has given the hair direction in accordance. These, of course, are "acquired characters"—the lie of the hair is in accordance with certain disposing forces of environment. Such causes do not act on us now; but there are no causes acting to the contrary in a sufficiently potent manner. Consequently, we retain by the conservatism of heredity a character acquired in response to the necessities of environment in our prehuman ancestors.

To return to the persistence of habit, the case of sucking may be noticed. Sucking, of course, is the act of childhood—it is one of the most important incidents connected therewith. The baby sucks to satisfy hunger; and associated with sucking are the feelings of warmth, sleep, and comfort. But hunger means distress; and sucking to satisfy hunger means sucking to alleviate a particular distress; consequently, it has developed into sucking to alleviate any distress or pain generally. Thus, when an infant is hurt, it turns in its distress to its mother; it desires to suck, and it forgets its trouble in sucking. All these associations are potent in later life. It may be observed in many children long after they have given up sucking; when they are cross, or when they are teased, or angry, and vexed, they suck their thumbs. Many children in the same way can not go to sleep without sucking something—their thumbs generally being ready implements for the purpose so persistent is the association of sucking with sleep. In later life children suck the ends of their pens or pencils when in doubt and perplexity over their lessons, from the association of sucking with distress or anxiety; and in still later life the masher, and the young man whose ideas do not flow very readily, suck the ends of their walking-sticks when they are in doubt or anxiety, in conversational or amatorial matters—such act of sucking being a relic of the baby habit acquired by the infant from the asssociationassociation [sic] of sucking with alleviation of distress, no matter in what way it was caused. Further, the number of men who suck the ends of their mustaches, and of women who suck the ends of their crochet or knitting needles, or anything else, whenever they have the least feeling of doubt, annoyance, anxiety, distress, discomfort, or the like, points to the persistence of a youthful habit long after all reason for it has ceased, and forms an instructive lesson in the development of the methods used to express emotions.

In other animals equally curious habits may be noticed,