The "call" to bowel movement is like the call of the alarm clock set to awaken one in the morning. If not responded to, it soon ceases to be heard. It is like the voice of conscience, which may be wholly stifled by continued disregard. This is only the operation of a general biologic law. A continuous sensation which is ignored, by and by fades out of the consciousness. For example, the clothing gives rise to no sensation unless adjusted in some unusual fashion, although in contact with almost the entire cutaneous surface. We are unconscious of gloves or shoes, although our hands or feet may be tightly compressed. So, if the "call" evoked by the pressure of feces upon the nerves of the rectum is not responded to, after the lapse of a certain time the "call" is no longer heard. A mass of feces may lie in the rectum, but it produces no sensation. The writer has many times found large fecal masses in the rectum of which the patient was wholly unconscious, although in some instances there was evidence that they had been present in the lower bowel for days or even weeks.
The first time a "call" is disregarded it will return again when additional fecal matter is pushed down from the pelvic colon by the stimulus of the next meal, or as the result of some other influence which excites intestinal action or increases intraabdominal tension. After having been disregarded or resisted many times, however, the "call" becomes less and less distinct, and by and by ceases entirely. The rectal nerves have lost their normal sensibility. They do not respond to the irritation produced by the contact of fecal matters, but have acquired a tolerance for such contact, just as the nerves of taste may become accustomed to contact with hot spices, so that they no longer cause any disagreeable sensation, or the skin may cease to react to a mustard plaster, so that a stronger irritant, as croton oil or a hot iron, must be required to produce a blister.
This condition of lost sensibility is one of the most common causes of constipation, and a condition which is sometimes very difficult to remove, although always conquerable by persevering effort, thanks to the great light thrown upon these cases by modern medical research.
To lose one's "call" is almost as bad as to lose a fortune; indeed such a loss has more than once led to loss of fortune, and to worse results. A "call" that has been lost must be most assiduously sought for until recovered, and put into efficient operation. The methods for accomplishing this will be described at length in a later chapter.
There are two factors which are chiefly active in producing bowel movements in normal individuals. The first is the practice of taking food only at stated intervals, regular meal hours. The second is regularity in the hours of sleep and morning rising. The omission of a meal, or a change in the hours of meals or of sleep will at once change or destroy the rhythm of bowel movements. Animals that eat continuously, as monkeys and barnyard fowls, have bowel movement many times a day.
The taking of food is the most active of all natural excitants of bowel action. When food is taken into the stomach, it produces powerful peristaltic waves which traverse the whole length of the intestine and carry the intestinal contents forward at a rate several times faster than the ordinary rate of progression; the larger the meal, and the more it is relished, the more pronounced is this effect. This explains the almost universal experience that the bowels move most freely and regularly soon after the morning meal.
On rising in the morning after a full night's sleep, so long a time has elapsed since the last bowel movement that the feces have accumulated in the pelvic loop and the descending colon, and it is only necessary that sufficient stimulus should be applied to cause feces to enter the rectum, and a "call" and bowel movement will follow. The act of rising, sometimes the mere awakening and the accompanying turning and stretching movements, are often sufficient to accomplish this. During sleep, the intestinal movements are slowed. The progress of the intestinal contents along the canal is at a much slower rate than during the waking hours. This is easily shown by X-ray observations after a bismuth meal. At the moment of awakening, all the bodily movements are quickened. The heart beats faster, the force of the breathing is increased, and the whole vital machine feels the impulse of quickened energies. If the pelvic colon has been slowly filling during the night, the various influences which are brought into play at the moment of awakening will be likely to cause the passage of a sufficient quantity of feces from the pelvic loop into the colon to produce a "call" and an evacuation.
Regularity of bowel movement is of the utmost importance. It is a function which should be assiduously cultivated. As we have seen, the periodicity of alvine evacuation is not the result of any mysterious influence, but is a product of forces which are largely in our own control and are easily understood.