Under the influence of diarrhoea' con ditions, the faecal discharges become much altered. At the onset, and persist ing so long as due attention is not given to the feeding, undigested food is always more or less present. Masses of casein are frequently seen, and may be easily recognized; fat may be present in small yellowish-white masses, somewhat re sembling the former in appearance, but distinguished by solubility in ether. Un changed starch may be recognized by the iodine test. The number of the dis charges during the twenty-four hours may vary from four or five to twenty or more. Their odor is probably dependent upon the character of the fermentation present. When sour, an acid fermenta tion, and, when very offensive, albumi nous decomposition is supposed to exist. The reaction is almost invariably acid; only when the discharges are more of an exudative than of a fmcal character does the reaction become distinctly alkaline. The color is very variable. The most noticeable change is to a varying shade of green, due, according to Wegscheider, to the conversion of bilirubin into biliver din. Lesage, however, states that this green color is not always due to bilivcr din, but is sometimes due to a chro mogenic microbe of which the pigment stains the stools; other observers, how ever, have not verified this statement. The amount of mucus is almost always increased, in some instances very largely so; when it is seen in quantity, it gener ally indicates a local congestion of the lower portion of the colon. Blood is oc casionally seen, due sometimes to ulcera tion, but more frequently to local con gestion and straining.
At birth, the intestinal tract of the in fant is free from bacteria. This condi tion, however, is quickly changed, and even in otherwise healthy infants, many forms may be found in the faecal dis charges a few days after birth. Under normal breast - feeding, however, and with good digestion, two varieties of bacilli arc constantly found, and, for this reason, have been termed the constant, or obligatory, forms of healthy-milk ffeces; they are the bacilli coli communes and the bacilli lactis aerogenes. The latter abound in great numbers in the upper part of the small intestine, where they appear to thrive in the yet-imper fectly-digested milk-curds. In the lower part of the small intestine and upper part of the colon they are met with in gradually diminishing numbers, while the bacilli coli communes, which in the small intestine are found only in com paratively small numbers, now multiply rapidly; so that in the lower part of the colon and in the fleces they greatly pre dominate over the preceding form and over other less constant varieties.
When breast-feeding is replaced by a more mixed diet, other forms of bac teria are found in variable numbers and in an inconstant way; among those fre quently met with are the streptococcus coli gracilis, various forms of micrococci, various liquefying bacilli, and the bacil lus subtilis.
In the discharges of diarrhoea some new forms make their appearance in great abundance, but, with the exception of the two before mentioned as always present, no one variety is so constantly met with as to permit it to be regarded as a specific cause. From several of these inconstant forms, however, Vaughan has isolated proteid substances, which when injected in very minute quantities under the skin of animals produce poisonous symptoms, such as vomiting and purg ing, with elevation of temperature, and in larger doses collapse and death. The question as to whether either of the ob ligatory forms under the abnormal con ditions met with in diarrhoea develop pathogenic properties, though much dis cussed, can scarcely be said to be defi nitely settled. Of one, the bacillus coli communis, recent studies indicate that it may undoubtedly at times develop viru lent pathogenic properties.
Booker, to whom the medical world is indebted for a careful investigation of this subject, states that in infantile diar rhcea the conditions for the development of bacteria in the intestinal canal appear to differ from those obtaining in the healthy intestine of milk-fed infants. The bacterial forms present a greater variety; forms met with only occasion ally and in small numbers in the healthy intestine are now much more pro nounced, and frequently appear in im mense numbers; while the bacillus coli communis and the bacillus lactis aerog enes become more uniformly dis tributed through the intestine. No single species of micro-organism is met with sufficiently frequently to he re garded in itself as the specific exciter of diarrhoea; but among the many forms encountered several varieties of strepto cocci and the proteus vulgaris appear to be of special importance. The strepto cocci are met with frequently; occasion ally seen in the stomach and upper part of the small intestine, they become much more abundant in the lower ileum and colon, especially in those cases where ul ceration of the mucosa is going on. So constantly and in such large numbers are they found in these cases that it is reason able to suppose that they play an active and important role in the ulcerative process. Of the proteus vulgaris, Booker says that it is found in more than half of the severer cases of diarrhoea; in the milder forms it is seldom met with. Cases in which this bacillus abounds present a different type of symptoms to those in which streptococci prevail; the patients more frequently show toxic phe nomena and have watery or pasty stools with a putrid odor, but without evidence of serious inflammatory trouble in the intestine.