Diseases of nutrition and infant feeding

Front matter

Class JT U"a, I & Book 'MCg_

%nghtN Li2jfi.

COPYRIGHT DEPOSIT.

Preface To Second Edition

The aim of the second edition remains the same as that of the first edition. New data have been added which brings the literature up to April 1, 1918. The exigencies of the war have retarded investigation to such an extent that during the past year there have been very few workers who were able to do anything to advance the science of Pediatrics. These recent publications have not been included in the literature.

John Lovett Morse, Fritz B. Talbot.

August 6, 1919.

Preface

This book was written to meet what seemed to the authors to be two distinct needs in American pediatric literature; a detailed description of the scientific basis of rational infant feeding and a description of the method of infant feeding taught in the Harvard Medical School. In it the authors have endeavored to meet these needs. It is intended to satisfy the demands, on the one hand, of those students who wish to become acquainted in the original with the data on which the scientific basis of infant feeding rests and, on the other, of the general practitioner who wishes to learn the clinical and practical sides of infant feeding. It is hoped that it will not only point the way to further investigations but also be of service to the clinician in his daily work.

John Lovett Morse.

Boston, Fritz B. Talbot.

September, 1915,

Section I Physiology And Metabolism

CHAPTER PAGE

I. Physiology of Digestion 1

II. The Digestion and Metabolism op Fat 20

III. The Digestion and Metabolism op Carbohydrates . . 32

IV. The Digestion and Metabolism op Protein .... 43 V. The Metabolism op the Mineral Salts 58

VI. The Energy Metabolism op Infants 64

VII. Bacteriology op the Gastrointestinal Canal ... 77 VIII. The Stools in Infancy 87

section II BREAST FEEDING

IX. General Considerations 99

X. Human Milk: Chemistry and Biology 103

XI. Clinical Considerations and Technique 134

XII. Wet-Nurses 153

section hi ARTIFICIAL FEEDING

XIII. Cow's Milk: Chemistry and Biology 157

XIV. Cow's Milk: Bacteriology and Chemical Tests . . . 175 XV. Sterilization, Boiling and Pasteurization of Milk . . 179

XVI. Certified Milk 189

XVII. General Principles op Artificial Feeding .... 192

XVIII. The Prescribing op Modified Milk 225

XIX. The Feeding of Premature Infants 250 x TABLE OF CONTENTS

Section IV Diseases Of The Gastrointestinal Canal

CHAPTER PAGE

XX. Spasm op the Pylorus 255

XXI. Hypertrophic Stenosis op the Pylorus 259

XXII. Nervous Disturbances op the Digestive Tract . . . 267

XXIII. Disturbances op Digestion 269

XXIV. Indigestion with Fermentation . 291

XXV. Infectious Diarrhea 302

XXVI. Constipation 321

section v DISEASES OF NUTRITION

XXVII. Rickets 329

XXVIII. Infantile Scurvy 341

XXIX. Spasmophilia 354

XXX. Acidosis 361

Index 369

DISEASES OF NUTRITION AND INFANT FEEDING

Chapter I Physiology Of Digestion Mouth

Food is drawn into the mouth of the infant by the negative pressure which results from the act of sucking. This negative pressure is between five and fifteen centimeters of mercury or between ten and one hundred and forty centimeters of water. 1

Almost all the work on the reaction of the oral cavity has been done by older writers and, although their results have not been uniform, it seems to be established that the reaction of the mouth of the new-born infant is neutral or weakly alkaline before the first food is taken. The acid reaction of the mouths of older babies is probably due to the breaking down of food remains. Oshima 2 has recently demonstrated lactic acid, by Uffelmann's test, in the mouths of infants, most often between the ages of three and six months. He attributes the presence of this acid to the action of a leptothrix. It probably is not present in large enough amounts to be of any practical importance. Immediately after birth a baby's mouth is free from bacteria, but it very quickly becomes infected. The normal bacterial flora, therefore, quickly gain entrance into the infant's gastrointestinal canal a few hours after birth.

The weight of the salivary glands at different ages, as given by Berger, 3 is as follows:

1 Gundobin: Die Besonderheiten des Kindesalters, Berlin, 1912, 248.

2 Oshima: Arch. f. Kinderh., 1907, xlv, 21.

3 Quoted by Gundobin: Die Besonderheiten des Kindesalters, Berlin, 1912, body

weight

Parotid

Av. wt. both submaxillaries gm.

Av. wt. both sublinguals gm.

Age

Av. wt. gm.

Max. wt. gm.

Min. wt. gm.

New born 3 months 6 months 2 years

1.80 3.18 4.50 8.60

2.4

4.8 5.8 9.6

0.9 1.4 3.1

8.2

0.84 1.53 2.12

4.89

0.42 0.84 1.05 2.00

These glands are heavier in healthy and well developed than in sickly and poorly developed infants, but considerable individual variations are often found. The glands begin to differentiate from the epithelium of the mouth in the second month of fetal life and can be dissected at the tenth week of fetal life.

Saliva is secreted during the first week of life and probably during the first day (Joerg, Bidder and Schmidt). It has the power of converting starch into sugar as soon as it is secreted. 1, 2> 3i 4 Ptyalin is present in both the parotid and submaxillary glands. 3 Ibrahim was able to demonstrate diastatic ferments in both the parotid and submaxillary glands of two fetuses. One of them weighed but 150 gm.; the other was in the sixth month of fetal life. He thought that there was about the same amount in each gland at birth. The diastase in the saliva is only able to digest starches as far as maltose and not into grape sugar. 5, 6> 7 Shaw 8 gave babies a test meal of barley water and washed out their stomachs from fifteen to sixty minutes later. He found that it was possible for the diastatic action of saliva to continue in the stomach as long as two hours after feeding. It is difficult to say what role the saliva of infants plays in the physiology of digestion. Probably it plays a very small part. In general, it has been shown, 9 ' 10 * 11>

1 Schlossmann: Jahr. f. Kinderh., 1898, xlvii, 116.

2 Montague: Diss., 1899, Leiden; Montague: Centralbl. f. Inn. Med., 1900, a, 705.

3 Schilling: Jahrb. f. Kinderh., 1903, Neue Folge, lviii, 518.

4 Moll: Monatsschr. f. Kinderh., 1905-06, iv, 307.

5 Musculus and Gruber: Zeitschr. f. Phys. Chem., 1878, ii, 177.

6 Musculus and Mering: Zeitschr. f. Phys. Chem., 1878, ii, 403.

7 Hamburger: Pfiuger Arch., 1895, lx, 543.

8 Shaw: Albany Med. Annals, Jan., 1904, xxv, 148.

9 Glinsky: Sitzung.d. Gesellsch. russ. Arzte zu. St. Petersburg, 1895. 10 Wulfson: Diss. St. Petersburg, 1898.

"Snarsky: Diss. St. Petersburg, 1901.

PHYSIOLOGY OF DIGESTION a

*■ 2 that the dryer the food, the greater the secretion of saliva. This rule, however, does not hold good with milk, 3 the food of babies, because considerably more saliva is secreted for a food containing milk than for that containing meat. It is admitted, 4 ' 5 however, that saliva may cause coagulation of milk and thus help stomach digestion. The amount of water, albumen, and mucus in saliva varies considerably.

Finizio 6 induced infants to suck bits of cotton and then determined the amylolytic power of the saliva. This was greatest about midday and was different in babies of the same age. When the babies were less than six months old, it did not vary after nursing or when starch was added to the food, but when they were over six months old, there was an increase in the amylolytic power immediately after a meal containing starchy foods. This increase was still noticeable an hour later. Beginning at about six months there seemed to be a gradual development of the specificity of function of the salivary glands. He tested the saliva of several babies monthly during the first year and found that the amylolytic power increased progressively from birth to the age of twelve months. At eight to ten months it was twice that at birth, and at one year a trifle less than that of children two to three years old. Allaria 7 found that, after the first weeks of life, the mouth reacted acid to litmus paper and phenolphthalein, and that the reaction was rarely neutral or alkaline.

STOMACH

The stomach of the fetus, with the exception of the pylorus, lies completely in the left hypochondrium. The pylorus is in the median line and is completely covered by the liver. These relations change after birth so that at fifteen months the liver no longer overlaps the stomach. The position of the stomach of the fetus is nearly vertical. In the newly-born child, it lies somewhat obliquely in the abdomen, and at the end of infancy, it has almost reached the transverse position.

The growth of the fundus compared with that of the stomach as

1 Malloizel: Jour. d. Physiol, et Pathol., gener., 1902, 547. 2 Heymann: Diss. St. Petersburg, 1904. 3 Sellheim: Diss. St. Petersburg, 1904.

4 Billard and Dieulate : Comptes rend, de la soc. de biol. a Paris, 1902. 6 Borissow: Russk. Wrat. 1903, Die, letzen 8 Arbeiten, quoted in NothnagePs Handbuch.

6 Finizio: Rev. Hyg. et Med. Infant, viii, No. 3, 224.

7 Allaria: Monatsschr. f. Kinderh., x, No. 4, 179.

a whole is relatively rapid during infancy. The length of the fundus of the fetus is one-fifth, of the infant one-quarter, and of the adult one-third of the total length of the stomach. 1

The stomach, as would be expected, grows rapidly in size during the first year. The greater curvature becomes longer, increasing 16 to 24 centimeters in length. Pisek and Lewald 2 conclude from their investigations with the Roentgen ray that there is no characteristic normal type of stomach in the infant. It is horizontal rather than vertical when compared with the adult type, and follows certain rather definite forms. They distinguished (a) the ovoid or Scotch bag-pipe type of Flesh and Peteri (b), the tobacco pouch (retort shape of Alwens and Husler), and (c) the pearshaped stomach with base above and to the left. The shape of the stomach does not depend on the amount or character of the food ingested, but rather upon the quantity of gas which it contains or acquires. Major 3 showed that the shape of the Roentgen ray picture of the stomach varied with the position of the infant and that the movements of the diaphragm could cause changes in its appearance. Alwens and Husler (quoted by Pisek 4 ) report, furthermore, that they have observed a change in the form from the tobacco pouch to the bag-pipe variety after the intestines have been emptied.

Gastric Capacity. — Recent investigations show that the anatomic gastric capacity, obtained by measuring the capacity of the stomach by water poured in post-mortem at a pressure of 15 cm. (the figures given in most text-books are based on such observations), is considerably smaller than the physiologic capacity. The physiologic capacity of infants' stomachs is at such variance with the anatomic measurements that it is safe to say that a baby can digest more than the anatomic size of the stomach would seem to warrant. 5

The following figures were taken from Pfaundler, 6 and represent the gastric capacity in cubic centimeters post-mortem with a pressure of 15 c. c. water.

^undobin: loc. tit., 264.

8 Pisek and Lewald: Am. Jour. Dis. Children, 1913, vi, 232. 8 Major: Zeitschr. f. Kinderh., 1913, viii, 340. 4 Pisek and Lewald : loc. tit.

B Mosenthal: Arch. Ped., 1909, xxvi, 761.

•Pfaundler: Magencapacitat im Kindesalter: Stuttgart, 1898, quoted by Gundobin.

Age of infant

Systolic stomach

210 200

235 230

290 295

360 365

Diastolic stomach.

The gastric capacity, determined post-mortem by Holt, 1 is as shown by Table 3.

Tables 2 and 3 represent the gastric capacity of infants with closed pyloric valves which allowed no food to escape into the intestine. Mosenthal investigated the gastric capacity of infants during life (physiological capacity) and post-mortem (anatomic capacity), and found that the former was always larger than the latter.

Age

No. of

Capacity

Age

No. of

Capacity cases oz. c. c.

cases oz. c. c.

Birth

1.2

6.88

2 weeks

1.5

10-11 "

8.14

2.0

12-14 "

8.90

2.27

3.37

4.25

4.50

14-18 "

5.00

5.75

The following table is a summary of the results which he obtained in a study of twenty-four cases:

Amount of milk offered at each nursing 4.0 oz.,

Amount of milk ingested at each nursing 3.6 oz.

Post mortem gastric capacity (Pfaundler's method) 2.6 oz.,

"In every instance, excepting the diastolic stomachs, the infant ingested more fluid at a nursing than the volume of its stomach, as determined by careful measurements, can contain." This means that the figures for gastric capacity given above represent the ana-

5 Holt: Dis. Infancy and Childhood, N. Y. and London, 1911, 309.

tomic capacity of the stomach, and that the physiologic capacity, what an infant can take at a nursing, can be considerably larger than this. This can be explained by the fact that shortly after milk is swallowed the stomach shows signs of motor activity and the milk begins to pass almost immediately into the intestines. This is proven by fluoroscopic examination which shows the milk spurting through the pylorus into the intestine before the meal is finished. This happens more easily with human milk than it does with simple dilutions of cow's milk.

Duration of Stomach Digestion. — The duration of stomach digestion has been studied for a long time, at first with the stomach tube, 1, 2 * 3 ' 4f 5 only, and recently with the Rcentgen ray. 6, 7 It can be said in general on the basis of these observations, that the stomach digestion lasts in the breast-fed baby from one and a half to two hours, and in the artificially-fed baby three hours. Pisek and Lewald believe that a large number of stomachs practically empty themselves within an hour, while A. H. Meyer, 8 and Von Monrad think that it is three and one-half hours before the stomach is emptied. A large meal obviously requires a longer period for digestion than a smaller one, and cow's milk remains longer in the stomach than human milk. 9

Ladd's 10 extended series of observations on babies, and Cannon' 11 on animals, have done much to increase our knowledge of this complicated subject. The infant's stomach, as compared with the adult's, shows a " curious lack of peristalsis." Shortly after food is ingested some of it may be discharged into the duodenum, without undergoing stomach digestion. It has been found in animals that carbohydrates leave the stomach the most rapidly of the three food components, a large part of them being discharged within two hours, while proteins are discharged less rapidly, and fats the most slowly. These facts fit in with the economy of the body, since carbohydrates are not digested at all by the gastric juices, and are, therefore, passed along to the small intestine as

1 Epstein: Prager med. Wochenschr., 1880, 45, 450.

2 Epstein: Prager med. Wochenschr., 1881, 33-34.

3 Epstein: Jahr. f. Kinderh., 1887, xxvii, 113.

4 Czerny: Prager med. Wochenschr., 1893, 495, u. 510 .

5 Wohlmann: Jahr. f. Kinderh., 1891, xxxii, 297.

8 Tobler and Bogen: Monat. f. Kinderh., 1908-09, vii, 12. 7 Leven and Barret: Presse Medicale, 1906, 63, 503.

9 Meyer, A. H.: Bibliothek f. Laeger, 8, R, III, 390-512. Kopenhagen, 1902. Ref. im Jahr. f. Kinderh., 1903, Neue Folge, lviii, 275.

Tobler and Bogen: Monat. f. Kinderh., 1908-09, vii, 12.

10 Ladd: Am. Jour. Dis. Children, 1913, v, 345.

11 Cannon: The Mechanical Factors of Digestion, London and N. Y., 1911.

quickly as possible; whereas the proteins, which are digested by the gastric juices, are retained for this action. The fats, on the other hand, are discharged from the stomach at such a slow rate that there is never any great accumulation of fat in the small intestine, the rate of the discharge from the stomach being approximately the same as that of the departure of fat from the small intestine. The discharge of mixtures of food depends upon the relative proportions of fat, carbohydrate and protein which they contain (Cannon). These findings in animals have been partially confirmed in a few observations on infants. In one instance, however, in which the infant received food containing no fat, 6.62% sugar, and 3.5% protein, the stomach was not empty at the end of 1]4, hours. If, however, a fresh feeding is given before the stomach is empty, the bismuth feeding is frequently pushed out into the small intestine by the second meal. Tobler and Bogen l also found that milk mixtures containing much cream pass more slowly through the pylorus than those with low percentages of fat.

Gastric Motility. — The motility of the stomach is in inverse proportion to the concentration of the food; in other words, the greater the dilution of the milk, the more rapidly the organ empties itself. 2 Carlson and Ginsberg 3 found that the empty stomach of the infant at birth, and of the prematurely born infant, exhibits the typical periods of tonus and hunger contractions of the adult. They conclude that in the normal mammal the mechanism of gastric hunger is completed physiologically at birth and is probably active sometime before term. These findings have been recently confirmed by Taylor, 4 who also concluded from his investigations that there is no appetite or psychic secretion of gastric juice in the young infant. In animals, the stomach is found to show signs of motor activity shortly after milk has been swallowed. According to the character of the movements of the gastric wall, two regions may be distinguished. The movements of the left hand, or cardiac part of the stomach, consist of slow, shallow, peristaltic waves, which gently push the food lying next to the gastric wall toward the pylorus. The cardiac part of the stomach acts as a reservoir, where the food lies undisturbed by any movement except such as is necessary to pass the peripheral

1 Tobler and Bogen: Monatschr. f. Kinderh., 1908-09, vii, 12.

2 Clark: Am. Jour. Med. Sciences, May and June, 1909, 674, 872. 8 American Jour. Phys., 1915, xxxviii, 29.

4 Am. Jour. Dis. Ch., 1917, xiv, 258; see also p. 254 of same for complete bibliography.

layer on to the pyloric half. The state of affairs is different in the right half of the stomach. Five to eight minutes after the ingestion of food, deep peristaltic rings advance toward the pylorus and press the gastric contents strongly against the pyloric valve. The valve opens from time to time and allows some of the food to pass into the small intestine. 1, 2 It has thus been shown by Cannon, in his Roentgen ray work on cats, that the two parts of the stomach have two distinct functions, the left, or cardiac half, acting as a reservoir, in which the food lies practically undisturbed until it is passed on to the right or pyloric portion. Here it is thoroughly mixed under greater pressure, and is finally pushed into the small intestine.

Tobler 3 was able to show, in a boy with a gastric fistula, that the coagulation of casein begins in from two to three minutes and is complete in ten minutes. This process is of great importance, since it is found that the fluid portion, containing the milk sugar in solution, is rapidly expelled from the stomach, while the curd, containing casein with fat entangled in its meshes, remains behind for further digestion. 4 Nature thus provides that too much fat is not set free at one time. The fluid gastric contents begin to pass through the pylorus before the infant has stopped nursing.

The cardiac end of the stomach has a very delicate mechanism of its own by means of which it is at times closed, at others open. In cats the cardia is alkaline. As soon as it becomes acid, the cardiac orifice closes and remains so until the neighboring food components become alkaline. 5 The pyloric valve acts in a manner directly opposed to that at the cardia. When the material in the antrum pylori is acid, the valve opens and vice versa 6 .

On the duodenal side of the pyloric valve an alkaline reaction allows the valve to open and an acid reaction causes it to close. Cowie and Lyon 7 found that the opening and closing reflex of the pyloric valve could also be demonstrated in infants. When the food was made acid the duodenal closing reflex is sustained and the evacuation of food from the stomach is consequently delayed, .even if the stomach contents are acid. Strongly alkaline food, on the other hand, causes the pyloric opening reflex to be delayed

1 Cannon: Am. Jour. Phys., 1898, I, 359.

2 Cannon: Am. Jour. Med. Sciences, 1906, cxxxi, 563.

3 Tobler: Verhandl. d. Gesell., Kinderh., 1906, xxiii, 144. 4 Moritz: Zeitschr. Biol., 1901, xlii, 565.

6 Cannon: Am. Jour. Phys., 1908, 1909, xxiii, 105.

6 Cannon: Am. Jour. Med. Sciences, 1906, cxxxi, 563.

7 Cowie and Lyon: Am. Jour. Dis. Children, 1911, ii, 252.

and as a result the food is retained longer in the stomach. Free hydrochloric acid is not necessary for pyloric opening in the infant, and it may provoke prolonged closing from the duodenal reflex.

Solid particles of food may be pushed against the pylorus without opening the valve 1 and it is supposed that the curd of milk will have considerable mechanical influence on the opening and closing of the pylorus, while fat, whey, and lactose have little or no mechanical action. Tobler 1 has also shown that the rapid inflation of a balloon in the duodenum checks the passage of food from the stomach. Cannon 2 believes that the evidence is opposed to the conception that mechanical agencies, acting either in the stomach or in the intestine, play an important part in controlling the normal gastric evacuation.

Influence of Posture on Digestion and Emptying Time of Stomach. — Owing to the anatomical position of the cardia, air which is swallowed while nursing is prevented from escaping from the stomach while the infant is in the horizontal position because food acts as a water valve. The air can escape if the infant is upright and, therefore, it is better to hold the baby upright after nursing or during nursing. Distension with air causes discomfort, prevents the infant from taking the proper amount of food and causes vomiting. 3

Fluroscopic examination of the stomach shows that the emptying time is markedly influenced by the position of the infant. There is comparatively slow motility in the supine position, and the stomach empties much more rapidly when the infant is on the right side than when it is on the left side. This phenomenon, which is almost constant, would seem to have clinical signifiance. It should prove to be of advantage to place infants on the right side when there is an evident delay in gastric digestion. 4

Secretion of the Stomach. — Pepsin has been found in the stomachs of fetuses born at four and six months, 5, 6 and is always present in the stomachs of babies born at term. 7 Breast-fed babies

1 Tobler: Zeitschr. Physiol. Chem., 1905, xlv, 185.

2 Cannon: The Mechanical Factors of Digestion, London and New York, 1911.

3 Smith and Le Wald, Am. Jour. Dis. Ch., 1915, xi, 261.

4 Hess: Am. Jour. Dis. Ch., 1915, ix, 461; De Buys and Henriques: Am. Jour. Dis. Ch., 1918, xv, 190.

6 Langendorff: Arch. f. Anat. u. Physiol., 1879. •Huppert: Wiener Sitsungsberichte, 81, Abt. 3.

7 Zweifel: Untersuchungen liber den Verdauungsapparat der Neugeborenen, Berlin, 1874.

secrete less pepsin than artificially-fed babies. Rennin is practically always present at birth. 1 There is no appetite or psychic secretion of gastric juice in the young infant. 2 Heubner 3 found lactic acid in babies' stomachs, but Sotow 4 and Hamburger and Sperk were unable to confirm these findings. A. H. Meyer explained these conflicting results when he found that lactic acid appeared within two hours after the feeding of mixtures of cow's milk, and that it never appeared after a test meal of tea, or a "water meal." This makes it practically certain that the lactic acid found in the stomach is not the result of gastric secretion, but of the action of the stomach juices or of bacteria on the food.

Engel 5 studied an infant of four weeks with a fistula in the upper duodenum, in which the connection between the stomach and duodenum was apparently cut off. The infant received nothing by mouth. Engel was able to collect from 100 to 200 cubic centimeters of gastric secretion per day by means of a small rubber tube passed through the mouth, and found in this pepsin, rennin, and free hydrochloric acid. He was unable to demonstrate a fat-splitting ferment or lactic acid. There is a difference of opinion concerning the presence of fat-splitting ferments in the stomach of infants from birth onward. Sedgwick 6 removed the stomach contents and fouud that they were able to split fat. This property is present at birth in rabbits and at a very early age in babies (in one case at two weeks) . Hess 7 found lipase in the stomach of the unfed new-born infant. As much as 25% of the fat in the food can be split by the gastric juices, although it is believed that under normal conditions less than this is split. In infants between one and four months old, the lipase content of the stomach increases with the age of the infant. 8 Gastric lipase is easily destroyed by free hydrochloric acid 0.2%. 9

Kramsztyk 10 found trypsin in a small proportion of the infants to whom oil test meals had been given. It is believed that this

1 Hamburger and Sperk: Jahr. f. Kinderh., 1905, Neue Folge, brii, 495.

2 Taylor: Am. Jour. Dis. Ch., 1917, xiv, 258.

3 Heubner: Jahr. f. Kinderh., 1891, xxxii, 27.

4 Sotow: Diss. St. Petersburg, 1895.

5 Engel: Archiv. f. Kinderh., 1909, xlix, 16.

6 Sedgwick: Jahr. f. Kinderh., 1906, lxiv, 194; also, Arch. Ped., 1906.

7 Hess: Am. Jour. Dis. Children, 1913, vi, 264.

8 Hahn: Am. Jour. Dis. Children, 1914, vii, 305.

9 Hull and Keeton: Jour. Biol. Chem., 1917, xxxii, 127.

10 Kramsztyk: Przeglad Pedyatryczny, 1909, i, 209.

tryspin has its origin in the pancreas and is regurgitated into the stomach. (Ibrahim.)

Practically all of the factors present in the adult digestion are present in babies, but in a weaker form.

Free Hydrochloric Acid. — Free hydrochloric acid is never found in the stomachs of some healthy breast-fed infants * while in others it is found regularly. 2 Hess 3 found it regularly in the stomachs of new-born infants even before food was given. Whether free hydrochloric acid is found or not in a given instance seems to depend upon the technique of the investigator. It may be said, in general, that the longer after a meal the stomach contents are tested, the more frequently hydrochloric acid is found. It is obvious that when a baby receives a food containing much casein, free hydrochloric acid will appear much later than when it receives a food which contains but little casein or other material with which hydrochloric acid can combine.

Dundin 4 found that the reaction of the gastric mucous membrane of the fetus was always neutral up to the sixth month, after which it was acid. He was unable, however, to demonstrate free hydrochloric acid in any fetus. Hamburger and Sperk 5 found small amounts in the stomachs of new-born babies from the third to the eighth day. The amount increases with the age of the baby (A. H. Meyer). About three times as much becomes " combined acid " on artificial feeding as on breast feeding. The acidity immediately after a meal is nil, but steadily increases during digestion, the rapidity of the increase varying directly with the age of the child. Free hydrochloric acid appears in a few minutes after a feeding of barley water. It does not appear, however, for an hour or more after a feeding of milk, the delay being due to the power of casein to absorb and combine with acid. Free acid appears later in disease than in health. 6 It is interesting to note that the breaking down of sugar into lactic acid is retarded by the presence of from .01% to .02% of hydrochloric acid and prevented by .07% to .08%. The power of casein to delay the appearance of free hydrochloric acid explains the fact that lactic

1 Heiman: Arch. Ped., 1910, xxvii, 570; Labbe: Rev. mens. d. mal. de l'enfance, 1879, xv, 401.

2 Cassel: Arch. f. Kinderh., 1890, xii, 175; Wohlmann: Jahrb. f. Kinderh., 1891, xxxii, 297.

3 Hess: loc. cit.

4 Dundin: quoted by Gundobin, Die Besonderheiten des Kindesalter, Berlin, 1912, 269.

6 Hamburger and Sperk: Jahrb. f. Kinderh., 1905, brii, 495.

7 Clark: Am. Jour. Med. Sciences, May and June, 1909, 672, 872.

acid is frequently present in the stomachs of babies fed on cows' milk. 1 ' 2 ' 3

The recent studies of Hahn 4 of the hydrogen-ion concentration of the gastric contents have added light from another point of view. He found that the acidity of the stomach juices, when studied in this manner, was strikingly constant being (H) = 1.0 X 10~ 5 . This is in striking contrast to the figures given above of the titrable acidity, and is considered to be the normal acidity of the stomach contents at the height of digestion, when the food is either one-third or two-thirds milk. He believes that this is the optimum acidity for the action of rennet and gastric lipase and that it inhibits the action of pepsin.

Our conception of the therapeutic action of alkalies in modifying gastric digestion has recently been changed. It has been claimed by Southworth 5 and others, on the basis of the work of Van Slyke and Hart, that lime water and sodium bicarbonate neutralize the hydrochloric acid secreted in the stomach, and thus delay the coagulation of milk by rennin. As the result of this delay a portion of the milk is allowed to pass into the duodenum before coagulation takes place. The amount of alkali given should be calculated in relation to the amount of milk and cream used in the mixture and not to the total quantity of the mixture, because the milk and cream alone contain casein and it is the casein which is acted upon by the rennin. This seems to be the most reasonable view to take at present. Clark 6 claims, however, that lime water does not reduce the acidity of the gastric contents, and that the neutralization of a portion of the acid is overcome by an increased stimulation of the gastric glands to form hydrochloric acid. The amount of acid available for digestion may thus be even increased. These findings presumably apply also to bicarbonate of soda. The evidence in relation to this subject is conflicting and it is by no means certain that the present conception of the action of alkalies will not be greatly modified by future investigations. The action of sodium citrate has recently been shown by Bosworth (see chapter on Chemistry of Cow's Milk) to be dependent in large part on reactions that occur in the milk itself. It changes the compound known as calcium caseinate into sodium caseinate. Sodium caseinate is changed by rennin to sodium paracaseinate,