only are these facts true of the voluntary muscles, but they may also be observed in similar phase in heart, lungs, stomach, and the organs of function in general. Swallowing an emetic causes vomiting, an effect brought about through muscular convulsion of the stomach for the purpose of ejecting a substance irritating to its nerves. The mere sight or thought of a disgusting object may have the same consequence, and imagination is oftentimes able to produce results like that occasioned by a powerful drug or by a combination of physical conditions.
Every organic act, healthy or diseased, is due solely to a current sent from one of the great nerve centers, and the latter may be called into being either indirectly by reflex action, or directly by feeling or thought. Though the mind and the emotions have large influence over physical functions, the field of operation over which that influence extends is comparatively little known. It is, in some respects, almost unbounded, for every bodily function may be hastened, retarded, or even totally suspended, and life itself may be destroyed by the subjective effect of thought. Pleasurable emotions are physically healthful ; painful ones the reverse ;
