Those diseases which we call in-born are merely the results of dis ease contracted in uteri). Anomalies of the heart and certain agenesic and hyperplastic conditions are either the results of some abnormal topographical conditions in the uterus (e. g., amputation by the cord), or of injuries during labor. Many malformations are correctly under stood to be dependent on the transmission of a pathological origin (as harelip and supernumerary fingers or teeth).
The newly-born infant, normal throughout, differs from the adult, as already shown, by its undeveloped condition. It reacts quite differ ently to the same surrounding conditions, and in a relative way to the origin and of disease. According to Escherich, one can differentiate certain periods ill the life of a child by the irregular progress in the growth of the above-mentioned undeveloped organs of the infant. In each of these periods the child will show a different susceptibility to disease. It will be best, in speaking of the pathogenesis of each period, to retain the usual classification. This is the one which used in his studies on the morbidity of different ages. We shall speak of an espe cial pathogenesis for the newborn, the stickling, the period of the first dentition (milk teeth), the period of the older child, and that of puberty. We will try to discuss pathogenesis front these points of view, and, as we have (lone in the Int roduction. give the features: Diseases of the Newborn. The diseases of the newborn, during the first week or two of life, are really little understood. In this short time. an exact picture of disease can scarcely be formed, so that it is usual to lay the cause of death on the undeveloped condition of the infant, unaccustomed to extra-uterine life. This is a perfectly fair con clusion, too, as the first two or three days is not a long enough interval for an infection \vhich might have occurred synchronously with birth to produce death. According to the statistics used by Eriiss, as an illus tration of the infant mortality during the first four weeks of life, almost one-half of all children die within the first week, and more than one half of these ,succumb by the first or second day. While we may have rightly concluded that the main cause of this high mortality is the unite .
veloped condition of the newborn child, we must not forget one of the most frequent diseases of this period. This has as its origin an injury of the navel, which one may call physiological. In the falling off of the cord bacteria may enter the navel and produce a severe infection.
Premature taking up the pathogenesis of the nursing child ("Saugling"), we must first speak of the premature baby. The most important. diseases that affect infants of this age depend on the child's not being accustomed to the demands; of extra-uterine life.
Such children, accustomed to the conditions of intra-uterine life, feel extra-uterine existence as an nphysiological stimulus. Their power of resistance is so lowered in this way, that the slightest disturbance may cause death.
The Nursling ("Saugling").--In the Introduction we saw in a general way the importance of the condition and function of the skin and of the mucous membrane of the respiratory and digestive tracts. The skin of children at this age is much more delicate than later, and so is less resistant to injuries. Trauma nevertheless plays no especial part, as the nursing child is usually carefully protected by its mother from any possible harm. Infants, however, show a general susceptibility for eczema and intertrigo, as a result of the decomposition of the urine and stools. Furunculosis also, which so frequently appears among infants, is caused, at least in part. by the sensitiveness of the skin. Other cir cumstances also, the chief of which is a generally lowered po Wel' of resistance, promote this tendency to furuneulosis. Such general circum stances as artificial nourishment, faulty feeding, dirt, and unhygienic surroundings tend to decrease the resistance. Other diseases are seen which depend on a markedly increased sensitiveness of the skin, called by Czerny the exudative diathesis. Such diseases appear widely spread over the body and show themselves in the superficial layers of the skin as a tendency to eczema, etc.
The chief task of the skin, as we have seen, lies not only in protect ing the body from the mechanical entrance of foreign substances, hut also in keeping the temperature of the body at a certain degree, in spite of the variations of the outside air. The skin is thus an organ which acts as a heat-regulator for the entire organism, and which in adults works with extraordinary exactness. In the nursing infant this regula tion of the temperature by the skin is moderately difficult, especially because the body surface in the child is relatively greater than it is in the adult. As a result of the cooling or overheating of the surrounding air, a very sudden lowering or raising of the body temperature may occur. Consequently, babies get very easily chilled, if the surrounding temperature is too low, especially in the first weeks of life. Moreover, they exhibit a, very rapidly rising temperature if the air is too warm. While this fact supports the theory that the vasomotor power of the skin, controlling the temperature of the nursing infant, is small, we also find that in febrile diseases the temperature mounts very high, because of the contraction of the vessels of the skin, which makes a great effect, owing to the relatively great body surface.