CHAP. I. SERVICEABLE ASSOCIATED HABITS. 37 \ ^ 'i •' and blowing the nose are completely under our com- ;v; \ mand. \ » When we are conscious of the presence of an irritating particle in our nostrils or windpipe—that is, when the » <• same sensory nerve-cells are excited, as in the case of sneezing and coughing—we can voluntarily expel the particle by forcibly driving air through these passages; ;* • hut we cannot do this with nearly the same force, * •; " rapidity, and precision, as by a reflex action. In this ^ \ latter case the sensory nerve-cells apparently excite ; t the motor nerve-cells without any waste of power by first communicating with the cerebral hemispheres—the , * seat of our consciousness and volition. In all cases '• i ^ there seems to exist a profound antagonism between the , *..; same movements, as directed by the will and by a reflex ' - stimulant, in the force with which they are performed and in the facility with which they are excited. As ;'; Claude Bernard asserts, " I7influen.ce du cerveau tend done & entraver les mouvements reflexes, a limiter leur force et leur dtcndue." n The conscious wish to perform a reflex action some- times stops or interrupts its performance, though the proper sensory nerves may be stimulated. For in- stance, many years ago I laid a small wager with a dozen < young men that they would not sneeze if they took !, * snuff, although they all declared that they invariably 7- did so; accordingly they all took a pinch, but from wishing much to succeed, not one sneezed, though their ] * •" eyes watered, and all, without exception, had to pay , '. I me the wager. Sir II. Holland remarks12 that atten- ' * tion paid to the act of swallowing interferes with the [ I proper movements; from which it probably follows, ! '* 11 See tlie very interesting1 discussion on the whole sub- ject by Claude Bernard, * Tissus Vivants,' 1866, p. 353-356. 13 'Chapters on Mental Physiology/ 1858, p. 85.