Desire can be set off in a woman either in response to a touch or by some act, sight, or thought which she has been exposed to. One of the chief things to which a woman responds is a cumulative tenderness expressed in words or in acts. Whatever the stimulus, however, the brain receives the signal and, through the nervous system, sends out preparatory reactions throughout the body. The response of men to stimuli perceived by the brain as sexual is amazingly fast; some men arrive at full sexual preparedness for intercourse within three seconds--that is, their penis becomes fully erect and ready to enter the vagina within that time. Women react, on the whole, somewhat more slowly, though full preparation for intercourse, under the best of conditions, is often only a matter of a few more seconds than the man’s. As the sexual excitement increases, tremendous changes go on throughout the body, changes that might frighten you if they occurred under other circumstances. The pulse rate goes up astonishingly. There are records of its reaching 150 and more as the individual approaches and then reaches the sexual climax. Such pulse rates generally occur, in health, only in athletes who are performing prodigious tasks of speed or endurance. The blood pressure, too, goes up precipitately. In a matter of a few seconds it can rise well over 100 points. Breathing also becomes much deeper and swifter. With the approach of orgasm the breathing becomes interrupted; inspiration comes in forced gasps and expiration occurs with a heavy collapse of the lungs. It is as though the sexually excited person had been in a race. As the sexual act continues there is a general shortage of oxygen throughout the body, which accounts for the unusual breathing. This gives rise to a tortured expression on the face, as if the person were undergoing severe pain. This fact has been observed by Kinsey in his famous study of female sexuality, and I quote here an interesting paragraph on the phenomenon: “ … Prostitutes who attempt to deceive (jive) their patrons, or unresponsive wives who similarly attempt to make their husbands believe that they are enjoying coitus, fall into an error because they assume that an erotically aroused person should look happy and pleased and should smile and become increasingly alert as he or she approaches the culmination of the act. On the contrary, an individual who is really responding is as incapable of looking happy as the individual who is being tortured.”