The conception of a "maternal impression" (the German _Versehen_) rests on the belief that a powerful mental influence working on the mother's mind may produce an impression, either general or definite, on the child she is carrying. It makes a great deal of difference whether the effect of the impression on the child is general, or definite and circumscribed. It is not difficult to believe that a general effect--even, as Sir Arthur Mitchell first gave good reason for believing, idiocy--may be produced on the child by strong and prolonged emotional influence working on the mother, because such general influence may be transmitted through a deteriorated blood-stream. But it is impossible at present to understand how a definite and limited influence working on the mother could produce a definite and limited effect on the child, for there are no channels of nervous communications for the passage of such influences. Our difficulty in conceiving of the process must, however, be put aside if the fact itself can be demonstrated by convincing evidence. In order to illustrate the nature of maternal impressions, I will summarize a few cases which I have collected from the best medical periodical literature during the past fifteen years. I have exercised no selection and in no way guarantee the authenticity of the alleged facts or the alleged explanation. They are merely examples to illustrate a class of cases published from time to time by medical observers in medical journals of high repute. Early in pregnancy a woman found her pet rabbit killed by a cat which had gnawed off the two forepaws, leaving ragged stumps; she was for a long time constantly thinking of this. Her child was born with deformed feet, one foot with only two toes, the other three, the os calcis in both feet being either absent or little developed. (G.B. Beale, Tottenham, _Lancet_, May 4, 1889). Three months and a half before birth of the child the father, a glazier, fell through the roof of a hothouse, severely cutting his right arm, so that he was lying in the infirmary for a long time, and it was doubtful whether the hand could be saved. The child was healthy, but on the flexor surface of the radial side of the right forearm just above the wrist--the same spot as the father's injury--there was a nævus the size of a sixpence. (W. Russell, Paisley, _Lancet_, May 11, 1889.)