Lacteal

“ As the food is absorbed through the walls of the alimentary canal, it is picked up by the rootlets of the mesenteric veins [5] and by the lymph channels,—the latter, through the abdominal cavity, are called lacteals. Nearly all of the fats are absorbed through the lacteals. The whitish color given to the contents of the lacteals, by the saponified fats, gives rise to the term lacteal, meaning “whitish.”
Nearly all of the proteins and sugars pass through the mesenteric veins and the portal veins into the liver. ”

“ There is no doubt that the small veins which ramify outside the coats of the stomach and intestines are capable of taking up any matters in a state of proper solution, even fats when dissolved in alkali. But are medicines ever taken up by the lacteal absorbents? Probably seldom or never; for it seems that these vessels are only engaged after a full meal, and subsequent to the regular formation of chyle. They do not exist in the coat of the stomach, but commence in the small intestine at some distance from the pylorus. ”

“ Hence in diabetes the lacteal system acts strongly, at the same time that the urinary lymphatics invert their motions, and transmit the chyle into the bladder; and in diarrhœa from crapula, or too great a quantity of food and fluid taken at a time, the lacteals act strongly, and absorb chyle or fluids from the stomach and upper intestines; while the lymphatics of the lower intestines revert their motions, and transmit this over-repletion into the lower intestines, and thus produce diarrhœa ”

“ I may here observe, by the way, that in every strong and healthy human fœtus we everywhere discover milk; it is particularly abundant in the thymus gland, though it is also found in the pancreas, through the whole of the mesentery, and in certain lacteal veins and glands, as it seems, situated between the divisions of the mesenteric vessels. ”

“ Sometimes we have crackers and milk. The lacteal fluid is usually twice skimmed, first for the teachers’ table (they have cream in their coffee in the morning) , secondly for the thin, anæmic fluid we get on our oatmeal. ”

“ The reaction of human milk is slightly alkaline; of cow's, neutral or slightly acid. The specific gravity of each is about 1.028 to 1.032. Human milk is sterile when secreted, but derives a few bacteria from the lacteal ducts. Cow's milk, as usually sold, contains large numbers of bacteria. Microscopically, human milk is a fairly homogeneous emulsion of fat, and is practically destitute of cellular elements. ”

“ Secondly, absorption is also effected by the lacteals, a set of vessels peculiar to the small intestines. These have their beginnings in the little villi just mentioned, side by side with the blood-vessels. These two sets of absorbents run in different courses, but their destination is the same, {97}which is the right side of the heart. The lacteals receive their name from their milky-white appearance. After a meal containing a portion of fat, they are then distended with chyle, which they are specially adapted to receive: at other times they are hardly discernible. ”

“ For nature never acts inconsiderately. In all the red-blooded animals, consequently, which require [abundant] nourishment, we find a copious distribution of mesenteric vessels; but lacteal veins we discover in but a few, and even in these not constantly. ”

“ Villi. 2. Small glands, called crypts.
B. Diagram showing structure of villi. 1. Small artery. 2. Lacteal. 3. Villus showing termination of the lacteal. 4. Villus showing capillaries. 5. Villus showing both the lacteal and the capillaries. 6. Small vein. 7. Layer of epithelial cells. Work of Capillaries and Lacteals.—The capillaries and lacteals act as receivers of material as it passes through the layer of epithelial cells covering the mucous membrane. The lacteals take up the digested fats,66 and the capillaries receive all the other kinds of nutrients. ”

“ Standard lard and standard leaflard are lard and leaf-lard respectively, free from rancidity, containing not more than 1% of substances other than fatty acids, not fat, necessarily incorporated therewith in the process of rendering, and standard leaf-lard has an iodine number not greater than 60. Milk is the lacteal secretion obtained by the complete milking of one or more healthy cows, properly fed and kept, excluding that obtained within 10 days before and 5 days after calving. ”

“ The lacteal system is a constant wonder: and it adds to other causes of our admiration, that the number of the teats or paps in each species is found to bear a proportion to the number of the young. In the Sow, the Bitch, the Rabbit, the Cat, the Rat, which have numerous litters, the paps are numerous, and are disposed along the whole length of the belly: in the Cow and Mare, they are few.163 And the teats of animals which give suck are exactly adapted to the mouth, particularly to the lips and tongue, of the suckling progeny. ”

“ The chyle, which is seen among the materials thrown up by violent vomiting, or in purging stools, can only come thither by its having been poured into the bowels by the inverted motions of the lacteals: for our aliment is not converted into chyle in the stomach or intestines by a chemical process, but is made in the very mouths of the lacteals; or in the mesenteric glands; in the same manner as other secreted fluids are made by an animal process in their adapted glands. ”

“ The Animal Lacteals take in their Food by the Pressure that is made from the Peristaltic Motion, and that Motion caus’d by the Action of Respiration, both which Motions press the Mouths of the Lacteals against the Mass or Soil which is within the Guts, and bring them into closer Contact with it. ”

“ It is probable that the lymphatics offers less resistance to the ingress of a mineral body into the system when it is presented to them in combination with some animal substance, which must alone be regarded as their peculiar stimulus, and the only matter which they are destined perpetually to receive and convey; for the same physiological reason, the lacteals may probably take up iron with greater readiness when in combination with vegetable matter, than when introduced into the stomach in a more purely mineral form. ”

“ The other constituent is the enzyme rennin, which clots milk; this property appears to be useful in that clotted milk will not pass the sphincter into the small intestine as quickly as it would if it were liquid, and so the digestive processes can go on in milk after clotting just as it goes on in any other of our foods. Since milk is the chief, and in many cases the only, food of the young it is of course very important that its digestion should be very efficiently carried on. As the food is churned by the stomach muscles, it becomes mixed with gastric juice. ”

“ The lesson of practicable importance that we learn from this is that the milk of one of the lower animals is not in its natural state quite suited to the delicate stomach of the growing infant, and that if it be substituted for the mother's milk it must be more or less altered, depending upon the age of the child. It is particularly important that sweet milk be taken slowly, as otherwise large curds, difficult of digestion, form as soon as it gets into the stomach. ”

“ Milk fat or butter is more digestible than almost any other fat, and its importance therefore can readily be realised. All the above constituents of milk fat are composed of different proportions of carbon, hydrogen, and oxygen, but milk also contains minute quantities of lecithin, a fat containing phosphorus in addition. Lecithin is also found in the brain and nerve material of animals, in the yolk of egg, and in several plants.
The nitrogenous constituents of milk—casein and albumen—are usually estimated together, and they are reckoned as of equivalent food value. ”

“ In a previous chapter it was found from comparing the analysis of mother's milk with that of cow's milk, that they widely differed in the proteins and sugar. The art of so changing cow's milk that it conforms as nearly as is possible to mother's milk is known as "modification." Where protein, sugar, and fat are given in proper amounts, healthy infants get along well; but when either the fats or proteins are given in excess, or when the digestion of the child is deranged, there is often no end of mischief. ”

“ In addition, sterilized milk is a different article from fresh milk, its chemical composition being altered by the process. The milk of the cow, when ingested, is changed upon encountering the gastric juices, into whey, a liquid, and into a tough mass of curd most difficult of digestion. To call milk a liquid food is absurd, for the solid matter in a pint of milk is equal to that in a half pound of meat, and in its dense coagulated form it is vastly more difficult of digestion. ”

“ With the fat, lactose makes up the bulk of the energy-producing material of milk, and while this is important it is only secondary when compared to the tissue-building power of the protein and minerals. Besides being an important part of milk itself, lactose is a valuable by-product in the manufacture of cheese. After being taken from whey, which is the clear, straw-colored liquid that remains when the curd, or coagulated portion, is completely removed from the milk, the lactose is refined and sold in the form of a powder that is used for various kinds of infant and invalid feeding. ”

“ Vomiting, griping, and diarrhœa, are so common among infants, and arise in general from causes apparently so evident, that, unless severe or of long duration, they rarely form the subject of minute inquiry. Hence these complaints are, perhaps, not so often attributed to deteriorated milk as they ought to be, although the fact of their occasionally originating from a morbid condition of this [Pg 52] fluid, (and therefore from protracted lactation as one cause of the latter effect,) is too well established to be questioned. ”

“ Besides which, we shall find that when from any cause whatever the nurse's milk becomes impoverished and deteriorated, even if this take place at an early period after delivery, the injurious effects already referred to may be produced in the child: for improper food, whether it be bad milk or any other inappropriate article of diet, is always calculated to derange the functions of the stomach, bowels, and other chylopoietic viscera, and in consequence to occasion disease. ”

“ Although flesh is a better chemical excitant, it is by no means a matter of indifference how it gets into the stomach. It must, therefore, be accepted that milk excites not only a really effective, but at the same time a very economic, secretion, and also that the appetite is unable to stimulate this secretion into a more active [Pg 274] or abundant flow. The secret of the relation of milk to the secretion of the digestive juices can, unfortunately, at present be submitted to no further analysis or investigation. ”

“ Fat occurs in milk as suspended globules, and by churning may be made into butter.
The Proteids include casein, albumen, lactoprotein, and a small quantity of globulin. These are the nitrogenous bodies.
Mineral Matter. The ash of milk, obtained by careful ignition of the solids, contains calcium, magnesium, potassium, sodium, phosphoric acid, sulphuric acid, chlorine, and iron, phosphoric acid and lime being present in the largest amounts.
(1) Lactic Acid Fermentation. If milk is left undisturbed, it is well known that eventually it becomes sour. ”

“ Attention must be paid to the cleanliness of the vessel, and care should be taken that the milk be that of ONE cow, and that it be new and of good quality; for if not, it will turn acid and sour, and disorder the stomach, and will thus cause either flatulence or looseness of the bowels, or perhaps convulsions. I consider it to be of immense importance to the infant, that the milk be had from ONE cow. ”

“ A tumbler and a half of warm milk (of a temperature of about 90° Fahr.) , in which half an ounce of cane, still better milk, sugar has been dissolved, and a bottle of skimmed cow’s milk, are then added.
“The addition of the sugar is made for the purpose of remedying the small amount of lactine in cow’s milk; the water is added to make the milk, which is rich in casein, thinner, and thus to facilitate its agitation and emulsion. Skim milk is used because it contains less fat, an excess of which interferes with fermentation. ”

“ Many mothers imagine that milk is so bland a fluid that it is impossible for an infant to take too much of it; but the fallacy of the notion is exposed when we recollect that milk is coagulated the moment it reaches the stomach, and that the real subject of digestion is curd—a substance not quite so light as milk has the appearance of being. ”

“ A child can take at least one quart in twenty-four hours. Watch the stomach and bowels for bad symptoms; if necessary you can put in one teaspoonful of lime water after the milk has been heated. If the child will not take milk, use one of the prepared foods. Mellins' malted milk, Borden's malted milk, peptonized milk, Imperial Granum, and follow the directions on the bottle. The different food waters mentioned above are to use when milk and other food preparations cannot be given. Albumen (white of an egg and water, not whipped) can be given and always cold. Cold milk also tastes better. ”

“ The diarrhœa infantum, or diarrhœa of infants, is generally owing to too great acidity in their bowels. Milk is found curdled in the stomachs of all animals, old as well as young, and even of carnivorous ones, as of hawks. (Spallanzani.) And it is the gastric juice of the calf, which is employed to curdle milk in the process of making cheese. Milk is the natural food for children, and must curdle in their stomachs previous to digestion ”