Iron is the most important of the mineral tonics, and may be more properly described as a food rather than as a medicine, being one of the most essential constituents of the red blood corpuscles. It exists normally in the blood in the proportion of 1 part iron to 230 parts red corpuscles, and in a state of health enough iron is taken with various kinds of food, to supply the demand. Beef especially, as an article of diet, provides iron, as it contains 1 part iron to 194 parts red corpuscles.
Iron has been called the great respiratory food. In the lungs it takes up oxygen from the inspired air, and carries it to all the tissues. No function of the body can be carried on without oxygen; the muscular system especially is dependent for its perfect activity on the presence of oxygen, and muscular power is in direct proportion to the efficiency of the respirations.
The feeling of tone and energy, both bodily and mental, which belongs to perfect health, comes from an ample supply of oxygen, and it is in this primary way that iron acts as a tonic; stimulates and strengthens the heart, nerves, and muscles; raises the temperature of the body and increases the appetite.
It is not absorbed by the unbroken skin, but on exposed tissue and mucous surfaces its action is astringent, coagulating the albumin of tissue and plasma, diminishing the circulation by compression of the vessels, and arresting hemorrhage. Iron is thus classed as a styptic or haemostatic.
Taken internally there is an astringent taste, and the tongue and teeth are darkened by a sulphide which is deposited as a result of decomposition. If given in excess or on an empty stomach it decomposes the digestive fluid, and acts as an irritant and astringent upon the mucous membrane.
The digestion or absorption of iron takes place partly in the stomach and partly in the intestines, and depends upon the presence, in normal quantities, of the gastric and intestinal juices.
Organic and inorganic compounds of iron are believed to be absorbed with equal readiness in the alimentary canal, principally in the duodenum, whence they pass to the spleen, where they are stored up, being given off to the blood later, and carried to the liver, where they assist in forming haemoglobin. Some part of the iron is afterwards taken into the blood, and is excreted by the caecum and large intestine. This is the prevalent view regarding the absorption of iron and its distribution throughout the system. Some claim that the inorganic iron combines with the sulphur in the intestines, forming the sulphide of iron which is excreted in the faeces, thus leaving all the food iron to be absorbed. Part of the food iron would be taken into combination, otherwise, by the sulphur, preventing absorption.
Iron has sometimes an irritant action on the bladder; its astringency in the alimentary canal causes constipation; and it is said that it decreases the secretion of milk in nursing women. An excess of iron is eliminated from the system in almost every possible way, but principally by the faeces, which it colors black by forming a sulphide.
The local irritant action of iron explains why it is always given well diluted and after meals.
In administering a course of iron, two things must be provided for:
1. The bowels must be loose.
2. The digestion must be good; and in the course of administration any one or more of the following symptoms may be noticed, indicating an excess in the system: frontal headache, slight disturbances of the digestion, irritation of the stomach or of the bladder, a feeling of weight at the epigastrium, constipation, a feverish condition. An acne of the face and chest is sometimes produced by iron, and the reduced iron causes eructations of gas.
It is very important to remember that all preparations of iron stain clothing, carpets, - in fact everything touched, and that the stains are with difficulty removed. Silver spoons should never be used for iron, but if they have been used, the stain will come off if rubbed with ammonia water undiluted. Oxalic acid will take the stains out of muslin or linen.