There is no doublt of this fact, as it appears in all official mor tality statistics with striking clearness. Even in localities where this is not so convincingly the case, as for example in Prague, where I have been able to demonstrate the absence of a maximum mortality in sum mer, a close study of the figures explains the reason of the exception. In these cases there is an artificial alteration of the conditions because the infants born in institutions, whose increase dominates the birth statistics, depart for the most part after a few days into the provinces, with a consequent reduction of the infant mortality. It is further established that in states and countries the population of which mainly nurse their babies, the mortality of infancy does not attain a clearly marked maximum in summer. On the other hand, in countries where there is much artificial feeding, the summer maximum is very high. If the population is considered according to wealth, taking the size of the dwelling as a standard, then it appears that the highest summer mortality of infants prevails among the poorer classes, a fact which is true among both the races which nurse, and those which do not nurse their infants. In hot weather, there occur digestive disturbances of a specially- severe type, while in the course of chronic affections of the digestive tract, acute exacerbations occur, which may lead to a fatal end. There must be circumstances of special significance to explain these facts.
'Under the influence of a high temperature outdoors, milk spoils easily, especially in the wretched quarters of the poor. This has been advanced as the chief cause of the summer cases, an opinion which has much in its favor. It does not explain everything, for it does not affect, for example, the summer gastro-enterie eases occurring in chil dren fed on breast-milk only, or on properly- sterilized cow's milk. Others assume as a cause that the heat so alters the digestive function, that an increase occurs in the virulence of the bacteria which have hitherto existed normally in the intestine. This is difficult to prove, and is not yet proven.
The relation between infant mortality and the state of the surface water is entirely- beside the point, as it has. nothing to do with the etiology of the summer diarrhceas.
Th. Meinert has expressed the opinion that the cause lies in over heating, a process analogous to the heat strokes of adults, an opinion which is supported in one of the recent publications by Illoway, an American author.
It is entirely certain that we cannot explain the causes of the regular appearance of summer cliarrInea, although it is an undoubted fact that the character of the food and sanitary surroundings have an influence upon the summer mortality of infants from diseases of nutri tion. This fact suggests that cleanliness and digestibility of the food, as well as careful hygiene, play the chief part in prophylaxis.
We should next consider the possibility of the acquirement of diseases of the digestive sy-stem by, means of contact infection. This results in an endemic prevalence of enteric troubles particularly in places where infants are crowded together, as in nurseries, foundling in stitutions, infant hospitals, and the like. Such epidemics have been reported in recent years from various localities, and have thrown new light on the prophylaxis and care of infants in institutions (Escherich, lleubner, Finkelstein-Baffin, et al.).
We have passed in brief review the various causes which ean produce diseases of nutrition in infancy. It remains, in concluding this part of the subject, to speak of the bacterial causes which play a primary Or .s•erondary part in the etiology of these disease, We are indebted to the work of lischerich, Tissier, and Alm.° for an apparently accurate description of the normal flora of the infant's intestine. The value of these results is somewhat limited by the fact that they are conclusive only with respect to the organisms present in the lower part of the intestine. The thorough study of the vital conditions and probable significance of these organisms in the course of normal digestion affords us a hope, that we shall soon be able to understand their pathologic variations and their significance in patho genesis. This has always been our pious desire. As suggested by Schmidt and demonstrated by Strassburger and others, comparative investigation of the intestinal content in stained cover-glass prepa rations, and on culture media, prove that a great many bacteria which can be demonstrated by staining can not be grown in cultures. Conse quently- the very- foundations of research arc not entirely solid. Very few processes have succeeded in finding bacteria which, by reason of almost exclusive recognition in the stools, penetration into the body, microscopically demonstrable eonnection with the intestinal lesions, pathogenicity toward animals, and the serum reaction, can be consid ered as actually proven causative. This holds good for hardly more than streptococcus enteritis (Escherich, Ifirsh, Libman!), Spiegelberg, et al.), colicolitis tEscherich), and pyocyaneus infections (Nob6court). To explain the findings in other cases it is necessary to assume the symbiosis of several varieties of organisms. In still other cases, in which. the normal bacteria were present in cultures in more or less purity (Baginsky, Booker), nothing better remains than to have recourse to increase of virulence (Lesage), formation of soluble poisons (Zaborsky), formation of food-decomposition products irritative to the intestinal mucosa (Baginsky), and other forced and badly proven explanations.