8i2 THE POPULAR SCIENCE MONTHLY. 



In tlie first category, the influence of mind in modifying is 

 chiefly confined to man. It must have acted from the time when 

 he first began to prepare his crude weapons of defense and offense 

 to the present day, when some new discovery or some new inven- 

 tion may alter the map of the world, revolutionize society, or give 

 one race or nation the advantage over another ; nor can we feel 

 sure that animals below man have not been modified by similar 

 psychical effort. In the second category, the direct influence of 

 the emotions on the individual, it is a psycho-physiological factor 

 involved in the question of use and disuse ; for if it be once ad- 

 mitted (and I think the tendency of modern neural science is in 

 the direction of establishing the fact) that strong mental effort 

 may be made to affect special parts of the body — i. e., that an ex- 

 cess of nervous force brought to play on any particular organ, or 

 any particular part of the organism, induces increased growth or 

 development of such parts ; we can understand how far desire, 

 especially under the spur of necessity, may be influential in in- 

 ducing modification. Lamarck's idea, therefore, may not be so 

 ridiculous as it has hitherto been supposed by many. Darwin 

 took no stock in this influence, and referred with some contempt 

 to the views of Lamarck and Geoffroy Saint-Hilaire. He thought 

 it strange that the author of "Les Animaux sans Vertfebres" 

 should have written that insects which never saw their eggs 

 should will them to be of particular form, which he thought 

 hardly less absurd than to believe that the desire to climb should 

 make a pediculus formed to climb hair, or a woodpecker to climb 

 trees. 



Emotion of Mother as affecting Offspring. — There may be some 

 doubt about the extent of the influence of the individual mind in 

 inducing direct modification, for the subject is a difficult one to 

 deal with, and we have few exact data to draw from. Since in 

 human affairs we recognize the power of will in affecting purpose 

 and action, and in molding character, it is legitimate to infer that 

 when our knowledge has increased we shall recognize its effect on 

 function. There can be less doubt as to the third category, viz., 

 influence of the mind or emotions of the mother on her unborn 

 offspring in inducing modification both physiological and mental. 

 As a cause of variation, though believed in by J. D. Hooker, as 

 we learn from the " Life and Letters," and by other of Darwin's 

 contemporaries, it was discarded by Darwin himself, his principal 

 reasons being that the results of observations made for him in 

 hospitals were adverse to any such influence. Medical men, as a 

 rule, also discard it as among the mere notions and superstitions 

 of women, and argue its impossibility on the ground that there is 

 no neural connection between mother and foetus. The ancients 

 practically recognized the influence of the imagination of the 



