THE SCOPE OF PSTCHOLOQT. 5 



Our first conclusion, tlien, is that a certain amount of 

 brain-physiology must be presupposed or included in 

 Psychology.* 



In still another way the pyschologist is forced to be 

 something of a nerve-physiologist. Mental phenomena are 

 not only conditioned a parte ante by bodily processes; but 

 they lead to them a parte post. That they lead to acts is of 

 course the most familiar of truths, but I do not merely mean 

 acts in the sense of voluntary and deliberate muscular 

 performances. Mental states occasion also changes in the 

 calibre of blood-vessels, or alteration in the heart-beats, or 

 processes more subtle still, in glands and viscera. If these 

 are taken into account, as well as acts which follow at some 

 remote period because the mental state was once there, it will 

 be safe to lay down the general law that no mental modifica- 

 tion ever occurs ivhich is not accompanied orfolloived by a bodily 

 change. The ideas and feelings, e.g., which these present 

 printed characters excite in the reader's mind not only 

 occasion movements of his eyes and nascent movements of 

 articulation in him, but will some day make him speak, or 

 take sides in a discussion, or give adAdce, or choose a book 

 to read, differently from what would have been the case had 

 they never impressed his retina. Our psychology must there- 

 fore take account not only of the conditions antecedent to 

 mental states, but of their resultant consequences as well. 



But actions originally prompted by conscious intelli- 

 gence may grow so automatic by dint of habit as to be 

 apparently unconsciously performed. Standing, walking, 

 buttoning and unbuttoning, piano-playing, talking, even 

 saying one's prayers, may be done when the mind is ab- 

 sorbed in other things. The performances of animai 

 instinct seem semi-automatic, and the rejlex acts of self- 

 preservation certainly are so. Yet they resemble intelli- 

 gent acts in bringing about the same ends at which the ani- 

 mals' consciousness, on other occasions, deliberately aims. 



* Of. Geo. T. Ladd : Elements of Physiological Psychology (1887), pt 

 m, chap. Ill, §§9, 12. 



