gastrointestinal tract. It is probable that a goodly proportion of these are cases of heat stroke.

While references to heat stroke in infants, in the literature, are by no means numerous, a number of cases have been reported by Illoway (21), Zahorsky (68), Snow (60), Finkelstein (9), Neuman and Japha (according to Reitschel) Rietschel (56), Liefmann and Lindemann (37), L. F. Meyer (46), and others. They were often breast-fed infants, were usually in good health, but for the most part of the fat, pasty type. In most instances some prodromal symptoms of restlessness and fretting have been present, after which the baby was taken suddenly ill, often in the evening, with loss of consciousness, high fever, hot skin, running pulse, and convulsions. The urine, when examined, was found to contain casts and acetone (in one case sugar, Finkelstein). With prompt hydrotherapy cures have been effected in many instances, while in others rapid death has ensued.

But, after all, only a small percentage of infants die during the summer in this fashion. Illoway estimates their number at 2 or 3 per cent, Finkelstein at 6 or 7 per cent of the total infant deaths in the summer. These are simple guesses for which there is no statistical verification.

Besides thermic fever we have two other types of affections especially fatal to infants in hot weather, (a) typical cholera infantum, running a rapidly fatal course with watery diarrhea, vomiting, fever, frequently convulsions, and (b) the subacute diarrheas which may last for days or weeks before a fatal termination.

It will be well, at this point, to run over the principal effects which have been noted as to the action of heat upon the human body.

Tolerance of heat.-With respect to adults, Rubner (58) found that temperatures in excess of 24° centigrade and relative humidities of 80 per cent caused symptoms of heat retention to make their appearance in adults. The experiments of Flügge, Paul, Ercklentz, and Heymann (13) have already been referred to as to the effects of stagnant air in setting up symptoms of heat retention.

Haldane (15) found that moderate work at wet-bulb temperatures in excess of 25.5° C. (78° F.) was impracticable by reason of symptoms of heat retention.

Effects of heat upon metabolism.-With rising temperatures the heat eliminated from the body by means of radiation and convection. becomes progressively less until a point is reached in which all the labor of heat elimination is performed by the evaporation of moisture. Ranke (53) points out that when the body has to choose between the quantity of food necessary for nutrition and that consistent with heat regulation, it is compelled to choose the latter in self-defense. As a consequence in hot weather the appetite is greatly reduced.

As a result of calorimetric measurements, Ranke found that, with mean temperatures of 25° C. the intake of food sank, in adults, to energy values, below those represented by the metabolism of the fasting, resting adult.

Another effect of heat is to depress the anabolic processes. Thus L. F. Meyer (46) found while the weekly gains in weight by the infants at the Berlin City Orphanage during the relatively cool months of July and August, 1910, were 590 and 600 grams respectively, in the very hot months of July and August, 1911, that these were but 290 and 350 grams.

Heat, sufficient to cause rises in the rectal temperature of the resting adult and other symptoms of heat retention has also the property of increasing the rate of metabolism. Sutton (61) found that in an adult exposed to relatively high temperatures (37° C.), in addition to the symptoms of heat retention, the respiratory exchange and the respiratory quotient were raised. He concludes that high temperatures accelerate the metabolism as heat does any simple chemical reaction. In this way a vicious circle is established.

Evaporation of moisture.-While it is a matter of common knowl edge that heat greatly increases the amount of water evaporated by the body, there is interest in referring to the amount of this loss. Hunt (20) found that with high dry temperatures (wet bulb around 70° F.) and exercise, as much as 134 liters of water were taken daily and the secretion of urine was then by no means free. In another series of observations he found that, in spite of frequent drinking, 16 hours were required to replace water evaporated from the body during a day's experiments in the hot room. In these latter experi ments the hemoglobin index of the blood was the same before and after exposure to the heat. Therefore the source of the water evaporated was the tissues of the body.

Effect of heat upon the digestive secretions.-There is evidence to show that the activities of the digestive glands, especially the stomach, are depressed by heat. V. Salle (59) found from animal experimentation that exposures to moderately high temperatures-29° to 31° C. (84.2° to 87.8° F.)-had the effect of greatly diminishing not only the amount of the gastric secretions but their acidity and digestive activity. In this way the stomach not only loses a portion of its power to act upon food, but from the diminished or absent acidity there is a corresponding loss in the antiseptic and antifermentative action of the gastric juice.

Effect of heat upon the resistance to bacteria.-The observations of Medowikow (40) show that exposure to heat has the effect of diminishing the resistance of young animals to bacteria in the intestinal tract. Medowikow exposed young rabbits to incubator temperature for 12 hours. He found at the close of the experiment that not only

were the bacteria in the intestinal tract increased but that in nine cases out of ten B. coli was present in the spleen or in the liver.

Effects upon the infant organism.-Let us now examine in what way the results enumerated above can be interpreted with respect to infants.

Metabolism of the infant.-In the first place the metabolism of the infant is keyed to a much higher plane than that of the adult. According to Nieman (47) the respiratory exchange of the infant is higher than that of the resting adult and corresponds to that of the adult doing moderate work. The total metabolism of infants is about 100 calories per kilogram and from 50 to 90 calories are required exclusive of the amounts retained for the purposes of growth. This corresponds to the energy quotient of an adult doing fairly severe muscular work.

Another evidence of the more active metabolism of the infant is shown by the skin temperature. Rubner (58) found that a thermometer placed between the skin of an adult's chest and a woolen undershirt registered about 32° C. Liefmann and Lindemann (37) state that thermometers inserted between the skin and clothing of infants registered between 34° and 35° C.

Since the metabolism of infants is higher, they produce much more heat than the adult in proportion to their weight. Though it is true that they have also a proportionately greater skin surface to provide for the elimination of this increased amount of heat, it must follow that when the escape of heat is prevented by meteorological conditions their greater rate of metabolism must favor heat retention.

Thermo regulation in the infant.-We can deduce from the above for the infant narrower temperature limits within which heat regulation is efficient than for adults, and consequently a more labile condition of temperature equilibrium. Experimentally such has proven to be the case. The observations of Generisch (14), Rietschel (57), Kleinschmidt (27), Heim and John (17), show that when infants are experimentally exposed to moderately high heat (28° to 32° C.) a rise in their body temperatures takes place. This rise was found to be greater in infants suffering from disturbances of the nutrition (Kleinschmidt, Rietschel).

Meinert (41) in his investigations in Dresden found that the rectal temperatures of infants in homes where the indoor temperatures were high were increased to 39° or 40° C., although according to the parents' statements the infants had been comparatively well.

Reduction of tolerance for food.-Another effect of heat is the reduction of the tolerance for food. Ranke's observations in respect to this effect of heat upon adults have already been mentioned. The adult, however, taking both solids and liquids, can diminish the one and increase the other.

Meinert (41) points out that in the breast-fed infant this demand for increased liquids is regulated by the breast, for as a result of numer ous observations he has found that breast milk is more fluid in the summer than in the winter. Indeed this is to be expected, as in hot weather the mother will instinctively drink more and eat less.

Besides this, v. Pirquet (51) also points out that not only the quantity but the quality of the food obtained by the breast-fed child is influenced by its appetite. In hot weather, when this is reduced, it quickly ceases to suck, hence it receives only the more fluid "foremilk," while the rich "aftermilk" remains in the breast.

The bottle-fed child is far more passive in this respect to its food, which it obtains with a minimum effort through the effects of gravity. It therefore varies its intake far less than the breast-fed child. Moreover, its increased thirst often leads mothers to satisfy it with additional food instead of water.

It is obvious under these conditions that bottle-fed babies are often relatively overfed in hot weather, a circumstance commented on by numerous authors.

Another effect of heat of importance to the digestion of infants is the diminution of the quantity, acidity, and activity of the gastric juice, as shown by Salle's experiments and the resistance of the intestinal tract to bacteria as demonstrated by Medowikow.

Not only will the digestive processes take place with greater slowness, thus favoring stagnation of the intestinal contents, but the deficient acidity of the gastric juice may doubtless permit pathogenic germs which would otherwise succumb to its acidity to gain access to the intestine. The diminished resistance of the intestine to bacteria would permit the proliferation of germs introduced in this manner or favor endogenous infections.

We see from the foregoing that there are a number of reasons why heat should exercise a particularly deleterious influence on infants. There remain for final examination the possible effects of heat in respect to cholera infantum and the subacute intestinal infections.

Effect of Heat in Producing Cholera Infantum.

Typical cholera infantum has always been regarded by the earlier American authors (cf. Miller) as a heat effect. The following reasons have been advanced by Meinert, Rietschel, and others for regarding it from this standpoint:

1. The severe form makes its appearance only after exposure to very hot weather or high indoor temperatures.

2. It often attacks infants hitherto in the best of health. Meinert found that 54 per cent of all the infants whose deaths he investigated had always enjoyed good health, while Johnston (24), from his observations in Leicester, places this at 75 per cent.