The second class of cow's milk saprophytes, which split up the proteffis (proteolytie), form spores, and are consequently resistant to heat. Therefore they ean grow and increase in a milk which has been freed from the acid producers by means of sterilization. We are indebted to the thorough researches made by Flugge and completed by Iffibbert for our knowledge of the fact that it is not always the poisons produced by the bacteria, but also substances contained in their pro toplasm, which are the active agents. Nevertheless, the clinical proof of the pathogenic action of the proteolytic bacteria in coNv's milk is wholly lacking. There are certain older and inconclusive statements, which have always been cited, such as those concerning Vaughan's tyrotoxicon, which has at present a legendary celebrity. With the exception of these, we possess no clinical observations directly proving injury to the infant from the taking of insufficiently sterilized cow's milk.
Recently Escherich has called attention to the possibility of infec tion from cow's milk, front the observation of an epidemic of enteric disturbance, in which he suspected a peculiar streptococcus as the cause. We have also at ottr disposal the interesting findings of Pet ruschky and Kriebel, supplemented by those of Czaplewski, Rabino witsch, and Bruning, which I can confirm from personal experience, that ordinary milk bought in the market shows in cover-glass prepara tions a remarkable richness in streptococei, which are not destroyed in pasteurization, and of which even the corpse.s can prove dangerous. Therefore we cannot exclude the possibility, that certain enteric affec tions can occur through cow's milk which has either been insufficiently, sterilized, or in which bacterial growth has been very active before boiling. Nevertheless we lack strict proof of this.
There are also a number of reports which suggest the probability that the fodder of the milk-giving animal may have some bearing upon the occurrence of diseases of nutrition in infants brought up on such milk. This ean happen in several ways. When cows are put out to pasture, the change causes looser dejecta, which afford a greater possi bility of infection than the more solid dejecta of the period of dry fodder. Also, certain fodder materials (brewer's grains, potato-peelings, turnip tops, etc.)• contain volatile substances which pass into the milk and irritate the gastro-enteric mucous membrane of the child. The view emphasized by Sotinenberger, that the eating of poisonous plants by grazing cows, and the passing of alkaloids into the milk is a cause par ticularly of very- severe gastro-enteric cases with collapse, has been repeatedly disputed. It has however been corroborated recently by
Plorkowski who reports that the demonstration of colchicine in the milk of such animals has been repeatedly obtained.
Also the water used in attaining a proper dilution may be of bad quality, and, through containing too much calcium oxide, nitrates, ammonia, glutinous substances, and the like, may cause injuries. Jfir gensohn has recently supplied some very interesting observations on this subject.
All these facts, which I have briefly reviewed above, brand cow's milk as a dangerous food, especially for the young infant, and as a food which plays an important part in the etiology of the acute and chronic diseases of the infantile digestive apparatus. The most -recent com pilation of our knowledge of this subject is found in the hook of Czerny and Keller, to which I have already repeatedly referred. This work, through original clinical observations and a thorough study of the lit erature, demonstrates the fact that c,ow's milk CAll be and very often is injurious, without the intervention of bacterial causes, or of biologic peculiarities, and without the passing over of poisons from the fodder, or the like. It demonstrates that certain constituents of cow's milk, in their absorption and assimilation, create disturbances in the metab olism of the child, which manifest themselves as severe injuries to its general condition, which may even threaten its life, and also act as rrritative symptoms of various kinds, referable to the digestive tract. A thorough description of these deviations front normal metabolism is given in another part of this text book, and I can therefore limit myself to the consideration of as much as is necessary for the under standing of the diseases of nutrition.
The above-mentioned authors select the term "milk-injuries" (111ilchniihrschaden) for group of digestive disturbances with well marked clinical characteristics. They, regard a too high fat content of the food as the cause of these injuries. Formerly a too high proteid content was considered the chief cause of the disturbances occurring in artificially nourished infants, and this view is still maintained by numerous authors. It is rejected by Czerny and Keller, upon plaus ible grounds,—an etiologic exclusiveness which is perhaps carded too far. At all events from their work, based upon the observations of a large material, it appears that cow's milk, even when properly ob tained, prepared and administered, can give rise to severe disturbances through the failure of a proper reaction of the infant's metabolism toward certain milk constituents.