This section of the book is from the "How and When to Be Your Own Doctor" book, by Dr. Isabelle A. Moser with Steve Solomon, published in 1997.
From The Hygienic Dictionary
Autointoxication.  the accumulations on the bowel wall become a breeding ground for unhealthy bacterial life forms. The heavy mucus coating in the colon thickens and becomes a host for putrefaction. The blood capillaries to the colon begin to pick up the toxins, poisons and noxious debris as it seeps through the bowel wall. All tissues and organs of the body are now taking on toxic substances. Here is the beginning of true autointoxication on a physiological level.Bernard Jensen, Tissue Cleansing Through Bowel Management.
I am not a true believer in any single healing method or system. I find much truth in many schools and use a wide variety of techniques. The word for my inclination is eclectic.
The most effective medicine in my arsenal is water fasting followed closely in potency by other, less rigorous detoxifying diets. Colon cleansing ranks next in healing power. In fact it is difficult to separate colon cleansing from fasting because detoxification programs should always be accompanied by colon cleansing. Further down the scale of efficatiousness comes dietary reform to eliminate allergic reactions and to present the body with foods it is capable of digesting without creating toxemia. Last, and usually least in effectiveness in my arsenal, are orthotropic substances (in the form of little pills and capsules) commonly known as vitamins or food supplements.
Interestingly, acceptance of these methods by my clients runs in exact opposition to their effectiveness. People prefer taking vitamins because they seem like the allopaths' pills, taking pills demands little or no responsibility for change. The least popular prescription I can write is a monodiet of water for several weeks or a month. Yet this is my most powerful medicine.
It is possible to resolve many health complaints without fasting, simply by cleansing the colon and regaining normal lower bowel function. Colonics take little personal effort and are much easier to get people to accept than fasting. So I can fully understand how perfectly honest and ethical naturopaths have developed obsessions with colon cleansing. Some healers have loudly and repeatedly (and wrongly) proclaimed that constipation is the sole cause of disease, and thus, the only real cure for any illness is colon cleansing.
Even though it is possible to have a lot of successes with the simple (though unpleasant to administer) technique of colon cleansing, degenerated lower bowels are the only cause of disease. I prefer to use bowel cleansing as an adjunct to more complete healing programs. However, old classics of hygiene and even a few new books strongly make the case for colonics. Some of these books are entirely one-sided, single-cause single-cure approaches, and sound convincing to the layperson. For this reason, I think I should take a few paragraphs and explain why some otherwise well-intentioned health professionals have overly-advocated colonics (and other practices as well).