It is probable that all forms of diarrhoea, with the exception of the diarrhoea of pure nervous origin, are dependent on the pathogenic action of the bacteria which are usually present in the bowels. These bacteria are divisible intotwogreat groups - (1) a large group, which abound in the small intestine, the caxum, and first part of the colon, which decompose the carbohydrates, with resulting formation of organic acids. These organic acids normally neutralise the alkaline intestinal juices and keep the contents of the small intestine acid. It is further believed that this acidity is of value in restraining the action of the putrefactive protein-decomposing bacteria to be now referred to; and (2) a large group of protein-decomposing organisms (Bacillus colt and others) which abound normally in the lower two-thirds of the colon, but under pathological conditions are present in the higher parts of the digestive tract. In all probability the diarrhoea which follows the ingestion of some irritating article of food results not from the direct action of the foodstuff, but from its indirect action in promoting abnormal bacterial growth. The different forms of inflammation (enteritis) and ulceration of the small and large intestines are undoubtedly of bacterial origin. These will be referred to later.

Diarrhoea may result from excessive fermentation and acidity in the small intestine, a condition which induces loosening of the bowels, flatulence, and colicky pains, or it may result from abnormal decomposition of proteins, due to excessive activity of the putrefactive bacteria. These are two distinct clinical types which can sometimes be differentiated. The former group must be treated by a reduction of the carbohydrates, and their replacement by proteins and fats; the latter require a milk or lacto-vegetarian diet for their correction. It must be recognised, however, that it is frequently impossible to decide whether the diarrhoea has its origin mainly in the small or the large intestine, and the condition has to be treated on the following general lines.

An attempt must be made to recognise the cause of the diarrhoea, which must be removed. In this, seek to determine whether the diarrhoea results from the derangement of the normal digestion of the carbohydrates in the small intestine, or of the proteins in the large intestine, as the dietetic treatment for the two varies in the manner already indicated. A study of the previous dietetic history of the patient, and of the nature of the symptoms and of the stools, will be of value in this direction. In cases of so-called "acid diarrhoea," the stools are very loose, acid, and usually yellow and frothy. In all forms the chief aim in treatment is to prescribe a diet of the least irritating character, one which will leave as little unabsorbed residue as possible. Articles of diet rich in cellulose - vegetables, fruits, coarse breadstuff's, malt liquors, and sugar - should be avoided. If the diarrhoea be severe, complete rest in bed is essential, and it may be necessary to withhold all food for a day or two, nothing being given but a little barley-water to allay the thirst.

When the symptoms have quietened down, or in milder cases from the outset, the diet should consist of arrowroot, cornflour, rice, sago, one of the patent cereal foods (p. 183), and milk. Milk must be given cautiously, and its effect noted on the stools; it is best given with lime-water, in proportion of three to one, to start with. Raw-meat juice, white of egg, the pulp of underdone meat, and special protein preparations, such as Panopeptone and Plasmon, are also useful. Thirst may be allayed by ice, cold weak tea, diluted red wine, or a lemonade drink.

Nervous Diarrhoea And Lienteric Diarrhoea

There are subjects in whom the entrance of food into the stomach excites an undue peristalsis of the whole bowel, with resulting diarrhoea (lienteric diarrhoea). Diarrhoea of essentially nervous origin is not uncommon, and this may be accompanied by a sudden influx of fluid into the bowel, with resulting profuse and liquid stools. There are many forms of nervous diarrhoea. None of them are specially influenced by diet. The condition must be treated on general lines. Frequently the patient is the best judge of his diet.