American Journal of Obstetrics and Diseases of Women and Children 20:1022-1028, 1887
Although the fact of premature birth is recognized by all writers on obstetrics, and the propriety of waiting to induce labor till the child is capable of independent life is insisted upon, yet an examination of many of the standard works on midwifery shows almost no suggestions as to the care of the child thus prematurely born. I deem the subject sufficiently important to direct your attention to some of the anatomical and physiological peculiarities of immature children, and to some morbid conditions consequent thereto.
There are numerous vitiating influences of ordinary life which predispose to premature birth, e.g., laborious occupation of the pregnant woman; or, at the opposite end of the social scale, an enervating life, alcoholism, phthisis, and some of the acute diseases whose evil influence results from the elevated temperature accompanying them, or from the defective oxygenation of the blood, or consequent placental anemia, although in a recent contribution to the pathology of pregnancy, Klotz  asserts that in the exanthemata a specific eruption on the mucous membrane of the uterus, inducing an endometritis, is the cause of the interruption of the pregnancy.
The effect of constitutional debility of either parent in determining premature delivery is clearly shown by Priestly,  and, as all know syphilis more than all else is the cause of too early birth.
Assuming that the child be retained to a viable age, the chances of its survival depend largely upon the character of the disease causing its expulsion; e.g., Runge  asserts that the intensity of fever and carbonization of the blood in acute febrile diseases will determine between a dead and living premature child; that is, a temperature may be sufficiently high and prolonged to interrupt gestation, but not to kill the fetus, and of course the effect of any influence which may disturb the normal pregnancy must be in proportion to its intensity; and an important fact influencing the fate of the child is that in premature birth the child is much more likely to present preternaturally, and it is well known that the dangers to the child are much greater than where the position is normal. Another proposition of much importance is that children vary in the degree of development at approximately the same age; admitting the difficulty of deciding the exact duration of a pregnancy, we have all been impressed with the difference in the size and weight of immature children.
There are certain conditions which are commonly regarded as indicating the age of the fetus. Thus a layer of subcutaneous fat is deposited during the last weeks, and nails grow to the ends of the fingers by the end of intrauterine life.
The testicles usually descend during the eighth month of fetal life, but you will recall cases where they did not enter the scrotum till long after birth.
In the Moscow Foundling Asylum,  all children are regarded as immature which weigh less than 2500 gm. and measure less than 45 cm. in length.
In an elaborate article upon this subject, Issmer (Archiv für Gynäk., XXX., 2) cites a large number of observers who nearly agree as to the normal weight and length of the mature newborn child, and he asserts that the length is a much more reliable and uniform standard than the weight.
The appearances of a premature child indicate its incomplete development; the subcutaneous layer of fat is imperfect; the skin, therefore, is wrinkled, the fine hair over the body is abundant, the nails do not reach the ends of the fingers, the muscular outlines are imperfect, the circulation is sluggish, and aeration badly performed; the color, therefore, is livid or yellowish. Several years since, Küstner  called attention to the fact that the presence of dilated hair-follicles caused by epidermal accumulation, producing at times a development of comedones on the nose, cheeks, and upper lip, were more abundant in prematures than in fully developed children.
He says: "Of twenty-five children, evidently not mature, comedones were remarkably distinct on the nose, and almost always were numerous around the mouth and eyes -- only one had few comedones and no milium. On the contrary, of sixty-five mature children, only two had milium to a decided degree, in a few they were barely perceptible, in the others not at all." And my own observation leads to much reliance on this condition as evidence of the degree of development.
Recognizing the premature child, a question of prime importance is as to its viability, which implies not merely being alive, but a capability of living. While no definite limit can be fixed, it may be asserted that there is no probability of life where the child weighs less than 1000 gm., or measures less than 27 cm. in length, where the greatest circumference of the skull is not 25 cm., and that of the thorax at least 23 cm., or where the circumference of the chest is not decidedly more than half the length of the child. 
Of course, exceptions to such rules occur. Tanner  says, "Jeffrey Hudson was only eighteen inches high at eight years of age... while Bebe, a seven months' child, was only between seven and eight inches long, and weighed a pound when born."
In estimating the probability of survival of a premature child, we should not be too much influenced by the supposed duration of its intrauterine existence, but also take into consideration the degree of development, vigor, etc., which it displays. Montgomery  cites two instances of children born before completion of six months' gestation who lived several months, and a number of cases where birth took place before seven months, in which the children had lived for years; and he quotes from Devergie cases of children born at full term who weighed but two and three pounds.
While every writer on obstetrics allows the probable fate of the child to influence his opinion as to the propriety of any operation by which pregnancy may be interrupted, it is remarkable how little attention is given to the child after its birth.
Tarnier,  however, does impress his readers with the importance of special care. He says: "All children born prematurely require the most special protection from cold; so that beside the usual clothing, the whole body -- the head and limbs especially -- should be enveloped in carded cotton, with hot bottles about it. The temperature of the room in which they are kept should be maintained at about 64° F." I decidedly object to this advice, "the usual clothing." Only the cotton should be used.
He says, "The temperature of the room in which they are kept should be maintained at 64° F." Certainly a very erroneous suggestion; when we bear in mind the temperature in which the fetus has lived, and its very limited calorifacient power, we should advocate a much higher temperature, from time to time the child ought to be exposed naked before a fire, and the entire body rubbed gently with the hand. The child should be laid on one side to obviate accumulation of mucus in the throat, from which, if it occurs, it should be removed by a camel's hair pencil or mop.
Hodge  says the child should not be fed with a spoon; now, from the weakness of the muscles of suction, the child is unable to draw milk from the breast and probably not from the bottle. I therefore believe spoon feeding to be the only proper method at first; the food given often and in small quantities, the mother's milk being the best nutrient.
Wiederhofer suggests pouring the milk through a tube passed by the nostril into the pharynx, as thereby the reflex movement of swallowing is more promptly excited. The child should be bathed only when absolutely necessary, and then by plunging it into warm water and immediately drying it with warm napkins; it should seldom be uncovered, as every movement or exposure brings it into contact with new cooler strata of air; because of the debility of the circulation it should not be allowed to lie long in one position, and to stimulate better respiration, efforts should often be made to induce fuller respiratory movements by tickling the feet, by careful inhalation of cologne water, weak ammonia, etc.
The practice which I advocate in all cases, of not ligating the umbilical cord until pulsation has ceased, is especially important in premature or feeble children.
The imperfect development of all the organs, necessarily implied by premature birth, contributes in various ways to peculiar morbid processes.
The small weight of the body compared with the area of cutaneous surface, and the absence of subcutaneous fat, makes the radiation of heat relatively much more rapid than in well-developed children, and on the other hand the production of animal heat is defective because of the imperfect respiration and circulation. From these defects arises an important clinical fact, viz., that serious morbid processes may occur without the usual elevation of temperature;  thus pneumonia may exist without fever, and, as shown by Soltman,  the reflexes are so defective in the new-born that no cough may accompany the pneumonia. From the absence of these two important symptoms, it may be very difficult to distinguish pneumonia from atelectasis, and from the feeble circulation hypostatic accumulations of blood are likely to occur, unless, as is often the case, the foramen ovale remains open, allowing blood to pass from the right to the left auricle. Atelectasis is especially favored by the feeble conditions of premature children; naturally the muscles are more feeble than in fully developed children; those of respiration, therefore, are incapable of expanding the thorax, inspiration is imperfect, and parts of the lung retain their fetal state. Of course, imperfect respiration implies defective oxygenation of the blood, which reduces the animal heat and further impairs the already limited vital powers. The original atelectasis is likely to be supplemented by acquired collapse of the lung, because of the bronchial catarrh which is likely to accompany these conditions. Kjellberg advises placing the child in a warm, moist atmosphere -- a suggestion I believe of practical value, not alone for the reason given. 
In consequence of the limited vitality of the immature child, it bears deprivation of food better than when mature, and it must be borne in mind when feeding them that they take much less food, 3 ij. - 3 iv. being all that they can bear at once. The digestive processes are defective; the food, therefore, is likely to be imperfectly digested and to excite enteritis, or from the feeble muscular power of the intestines constipation may exist. Of course, predigestion of the food suggests itself as an important preventative of the evils mentioned.
In the kidneys, uric acid infarcts occur because of the defective circulatory and respiratory processes; they may lead to suppression of urine, renal colic, or organic disease of the kidneys, and as the excretory glands of the skin are not developed until late in intrauterine life, they may be incapable of eliminating the elements of urine from the blood, and uremia will then result. The various changes in the skin subsequent to birth are much slower in their progress; therefore, desquamation and shedding of the fine hair continue longer, and because of the feeble circulation sclerema often occurs. The investigations of Laugerts (quoted by Miller) have shown that the subcutaneous fat of infants contains a large proportion of palmitic acid, 31%, while that of adults contains but 10%, and that a slight fall of temperature causes the acid to solidify and thereby sclerema occurs.
Icterode color of the skin is almost universal in premature infants, and continues longer than in mature infants;  the greater frequency of this icterus is explained by Birch-Hirschfeld by the feeble circulation and the defective action of the right heart, in consequence of which venous congestion of the liver occurs, resulting in swelling of that organ and compression of the gall-ducts. The toxic effect of retention of biliary elements in the blood is fully recognized, and destruction of blood-corpuscles, with the consequent impaired nutrition of the muscular and nervous tissues, and depression of temperature, may be due to this cause.
The separation of the umbilical cord takes place much later in unripe children, sometimes being delayed for two weeks, and even then the stump may contain fluid having septic qualities; the blood is deficient in fibrin and consequently forms thrombi less perfectly, so that bleeding from the stump occurs more readily, or the loosely formed clot more readily undergoes decomposition and causes septic processes.
The nervous system of such children is very imperfect, and reflex actions are with difficult awakened; the cerebrum is very soft; gray and white substances are scarcely distinguishable, and the convolutions and sulci are but slightly marked.
The usual decrease of weight after birth is exaggerated in the premature, and the commencement of increase is much later than normal.
 Archiv für Gynäk., xxix., 3.
 London Lancet, 1887.
 Volkmann, Vorträge, 174.
 Th. Miller, Jahrbuch für Kinderh., xxv., 3.
 Archiv für Gynäk., xii., 102.
 Miller, loc. cit.
 "Signs and Diseases of Pregnancy," p. 218.
 "On Pregnancy," p. 423.
 Cazeaux and Tarnier, "Obstetrics," ii., 1,022.
 "Sys. Obstetrics," p. 13.
 Th. Miller, loc. cit.
 Jarbuch Kinderh., xi., 1.
 Kjellberg, Jahrbuch Kinderh., vi., 1.
 Epstein, Volkmann, Vorträge, 180.