In the last year or two a valuable method of treatment by means of soured milk and other methods of administering selected lactic germs has been brought to the notice of the profession by the distinguished French bacteriologist, Eli Metchnikoff, of the Pasteur Institute, Paris. Treatment by this means has lately become a fashionable craze, and as is usual when a new method of therapy is introduced, exaggerated claims have been made for the treatment. While our knowledge of this method of treatment and of its limitations is by no means complete, clinical experiences has abundantly shown that this form of treatment is a real and important advance in therapeutics, and very specially in intestinal bacterio-therapy. It is therefore advisable to give a short account of the rationale of this treatment as laid down by Metchnikoff. It is well known that the food exerts an influence on the bacteria normally present in the intestine.

This dependence of intestinal microbial growths on the nature of food is due to the fact that certain bacilli secrete substances which render the soil unsuitable for others, so that by selecting an organism which is innocuous to human beings we are enabled to destroy active germs productive of injurious effects. In order to attain this we must secure if possible an antiseptic mechanism which, once started, will maintain its effect, and this can only be accomplished by the services of a living organised ferment. It is well known that lactic acid is a powerful anti-putrefactive agent. When milk turns sour, that is to say, when the milk sugar has undergone lactic fermentation with the formation of lactic acid, it can then resist putrefaction for a long time. This fermentative action is due to the lactic acid, and the knowledge of this fermentative property, first shown by Metchnikoff, induced him to employ cultures of the lactic germs in order to produce nascent lactic acid just where its action is required. The product by which this result is achieved is known as "Lacto-bacilline".

Fresh micro-organisms are continually being ingested with uncooked food, and these intensify the effect of pre-existing colonies in inducing putrefaction of the intestinal contents and noxious fermentations, more particularly the butyric fermentation. Sour milk, owing to its containing lactic acid, can prevent butyric fermentation and putrefaction, both of which are capable of causing various disorders in the human organism, and it has thus been applied to hinder decomposition changes in the digestive tract. The experiments by Herter of New York and other investigators have clearly established that lactic bacilli markedly diminish the putrefactive process. This has been determined by careful examination of the amount of decomposition products (in disease, etc.) in the urine, when selected species of lactic ferments were administered in the form of curdled milk and other means. In some observations by Cohendy, examination of the faeces demonstrated the presence of lactic germs, which continued to multiply long after the administration of curdled milk had been abandoned.

In endeavouring to combat intestinal putrefaction, instead of giving lactic acid, which is oxidised or excreted by the kidneys, it is better to introduce the living germs into the organism, either in the form of Lacto-bacilline powder or tablets,or, if preferred, as soured milk. These germs continue to multiply in the intestine, and as they are amply supplied with the sugar necessary to their maintenance, they set free lactic acid, which permeates the intestinal contents and inhibits putrefaction and all irregular fermentation. It is well known that certain races in Asia and Russia make habitual use of curdled milk, which constitute their staple food, and this itself may be taken as a guarantee of the value of this food. It might be supposed that of the many varieties of curdled milk in daily consumption throughout the world, any one of them would answer the purpose of arresting intestinal putrefaction, but as a matter of fact this is not so. Raw milk may contain in addition fungi, which favour the development of pathogenic bacteria; it may also contain tubercle, and other bacteria which are not neutralised by the lactic ferment. In most cases, therefore, it is found more convenient to give the lactic ferments in the form of Lacto-bacilline powder or tablets. Milk in order to undergo thorough lactic fermentation must have the organised ferments - the living microbes - added to it. This is added in the form of pure cultivation of lactic germs, which may be given in the form of Lacto-bacilline powder or tablets, and this may be given without having recourse to milk as the vehicle. The special bacillus used by Metchnikoff, described as the Bulgarian bacillus, is a very active producer of lactic acid, coagulating milk within a few hours, and curdling it without the assistance of any other organism. Since too large a proportion of fats may not be desirable, the curdled milk may sometimes be made with advantage from skimmed milk. Having been boiled and cooled, the milk is inoculated with a sufficient quantity of a pure culture of lactic germs (Lacto-bacilline). When fermentation is complete, it yields a curdled milk which is agreeable to the palate and tends to diminish putrefaction. Taken in doses of from a pint to a pint and a half daily, this product regulates the intestinal functions and also prevents disease. When milk is treated in this way a large proportion of the casein is rendered soluble, and a still greater proportion of the phosphate of lime has its solubility similarly increased. This proves the easily digestible qualities of curdled milk prepared with pure cultivation of lactic microbes. Curdled milk is therefore both a food and a medicine. As its preparation requires a little time and trouble it is found more convenient to administer lacto - bacilline in powder or tablet form, mixed with boiled milk, or even in water. Reference is later made to the unreliability of the commercial forms of lacto-bacilline in common use.

Diseases Benefited By Lactic Bacilli Therapy

From an extensive experience of this treatment carried out under conditions specially directed to test its efficiency, the author is satisfied that it is a valuable addition to our therapeutic resources. Certain cases of chronic intestinal catarrh, pernicious ansemia, subacute and chronic nephritis, rheumatism, and gout are very strikingly benefited. The treatment is of special value in cases of auto-intoxication, resulting from abnormal putrefaction of proteins; it has little value in cases due to carbohydrate fermentation.

Methods Of Administration

It may be given as buttermilk, which is the residual milk left after churning and removing the fat; or as soured milk, which differs from buttermilk in that the fat has not been removed; or in the form of one of the many commercial preparations1 of lactic bacilli at present in the market, e.g., Lacto-bacilline, Sauerin, Lactigen, Trilactinc, which are added to milk for the preparation of an artificial soured milk. Unfortunately these preparations cannot be implicitly relied on, as it has been found that they may contain no active lactic acid bacilli. The writer recently gave a demonstration of the results of the bacteriological analysis of many of the preparations in everyday use, at which it was shown that many of them contained no active lactic bacilli (although other bacteria were numerous), and had not the property of souring milk in twenty-four or forty-eight hours. Other observers have had the same experience. Of the preparations recently examined, Sauerin and Lactigen have given the most satisfactory results. When a freshly made buttermilk from a good source is obtainable, this is probably, on the whole, the safest method of administration. Here again, however, we have to boar in mind its uncertain composition. The "strain" of germs used in the preparation of commercial buttermilk is, as a rule, renewed every three weeks; as the strain gets attenuated, there is a corresponding increase in the numbers of other bacteria present in the milk, and the presence of these may interfere with the action of the lactic germs present. In the same way, if milk has been doctored by the addition of preservatives, the curdling may be prevented even although the lactic bacilli are active. There are also specially prepared buttermilk preparations in the market made from the Bulgarian bacillus, e.g. "Fermcnlactyl," made by the Aylesbury Dairy Company. Bulgarian soured milk chocolates (Rowntree's), and a cheese containing lactic bacilli in large numbers (Lactic St Ivel cheese), are other forms in which the lactic germs may be given. Under the influence of the administration of an active preparation of lactic acid bacilli in favourable cases, a very notable improvement in the state of the stools is brought about; these lose their feetor and become formed, presenting a marked contrast to the extremely foetid, pultaceous stools originally present. It will readily be understood that lactic acid producing germs are more likely to have a beneficial effect when the diet is simplified along lines such as are laid down in the section on Auto-intoxication, p. 346.

1 All the makers supply detailed instructions for the special methods of preparation.