DISEASES OF THE MOUTH - The cavity of the mouth is very small and narrow, conditioned chiefly by the lack of teeth, 60 peculiar to this early age, and the strong development of the tongue.
The salivary secretion is very scant during the first weeks of life, in consequence of which the mouth is relatively- dry. With the develop ment of the first set of teeth the secretion of the saliva becomes more active, because the upward growth of the teeth produces a sensible irritation of the dental and alveolar branches of the trigeminus and reflexly stimulates the salivary glands to activity-. In the second half y-ear a marked increase in the quantity of the saliva accompanies the eruption of the teeth.
The ptyalin of the saliva is demonstrable even in the newborn infant (Schilling), but does not exhibit any great diastatic power until near the end of the second month (Zweifel, Korowin).
In general the reaction of the oral fluid is appreciably acid, while the product of the salivary glands obtained with strict precautions gives a weak alkaline reaction. The acid reaction is produced by the fermen tative processes of bacteria, which find favorable conditions for life in the warmth of the buccal cavity and in the presence of milk particles.
The characteristic ingredient of the saliva in the adult, namely, potassium sulphocyanide, is entirely absent in the secretions of the mouth in the first months of life.
The absence of teeth and the deficient salivary secretion plainly show us that the organs of the mouth in the infant can not meet the demands which are required at a more mature age. On the other hand, we recognize precisely in this backward development a judicious arrange ment for the act of nursing, the most important function of the infant's mouth. The several organs of the mouth in the normal infant are more or less specifically modified in this direction. Not only the fleshy, bulky charaeter of the tongue, which makes the inspection of the faucial walls difficult, but also the strong resistance which the masseters of the newborn infant usually show 011 attempting to open the mouth forcibly, indicate that the organs concerned in the act of sucking are already highly developed at this very early period.
Ranke has endeavored to explain the "corptactilimiadipasnm" as a supporting organ to the act of sucking. This fatty body in the cheek of infants was first described by Geheve, a pupil of Walter. It is a circumscribed mass of adipose tissue, suppEed vith a movable attachment, and on both sides it is so situated that it lies immediately over the buceinator and masseter muscles. According Ranke, its biological significance is that of a nursi n g cushion ("saugpolster"); in other words, it serves as a bolster for the buccinator; by stiffening its substance it gives support to the function of the cheek dining the act of nursing (Fig.1).
Indeed, it is very remarkable that this accumulation of adipose tissue, which is especially noticeable in atrophic infants, should retain its original volume even in cases of extreme emaciation; which fact, judging from the gradual involvement of the organs in the process of inanition, seems to indicate that it has some function very essential to life. This is the chief reason why Ranke assumed the nursing-cushion to have a very important function which otherwise would seem obscure judg,ing from the modern view of the nursing mechanism.
Furthermore, a judicious adaptation to the act of sucking is found in the strong development of the levator i superioris muscle and the ragged prominences on the inner mucous membrane of the lip which are about 1 rn. in length and were first described by W. Krause. These atrophy after serving the purpose of applying the mouth closely to the nipple.
The mechanism of the sucking aet (Auerbach, Escherich, Pfaundler) occurs in two alternating stages. The first stage consists in the depression of the tongue and lower jaw, after the jaws, tongue and lips have en closed the nipple airtight. Through this act the oral caxity is enlarged and, as the dependent soft palate closes the faucial opening, a negative pressure is produced in the mouth. The first action serves to grasp the mammilla and draws the milk into the outer lactiferous passages.