Enemata. - A different class of administrative operations consists in injections into the rectum, which injections may be purgative, anodyne, nutrient, emollient, astringent, anthelmintic, etc. For speedy and efficient cleansing of the large intestine the purgative enema is of incomparable value, care being taken that the quantity of the injection be sufficient, that it be passed up as far as possible, and that it remain as long as the patient is able to retain it.

Nutrient enemata may be employed when, for any reason, the food cannot be made either to enter the stomach or to remain there. Small quantities - 3 or 4 ounces - are retained better than larger amounts. As the mucous membrane of the rectum does not have any digestive power, such enemata should be predigested, either by peptic or pancreatic ferments. Milk, oatmeal, gruel, oysters, eggs and milk, peptonized, with mild alcoholic additions, as of sherry, make excellent nutrient enemata.

Another mode of securing beneficial results from internal administration through the absorptive properties of the intestine is by means of suppositories, readily introduced within the sphincter ani and dissolving at the temperature of the body. This method of medication is serviceable either for local or general purposes.

To take the place of intravenous injection, normal solution, 0.6 of 1 per cent., is used as an enema in all conditions where the former is indicated, especially after major operations. From 7 to 17 fluidounces (207-503 Cc.) are injected, according to the individual tolerance of the patient. These injections are to be repeated in the endeavor to secure the absorption of from 2 to 6 quarts (liters) of the solution in the course of twenty-four hours.

Conditions Modifying the Action of Remedies. - All individuals are not affected in the same degree by the same remedy. Age, size, weight, fatness or leanness, sex, temperament, etc., are some of the variants. These may be considered under the general head of dosage.

Dosage. - The term dose implies the quantity of a medicinal agent which under certain conditions it is advisable to administer. In other words, the therapeutic dose is that portion of a medicament which is capable of producing the required action. There are many considerations entering into the question, to be weighed by the features of the individual case. Dosage may be regarded as perhaps the most vulnerable point in therapeutic science, yet one upon which the art of healing almost wholly depends. While it yet seems advisable to state in a text-book the so-called maximum and minimum doses of various drugs, clinical experience has convinced me that the principle of the maximum and minimum should not be considered the true rule for dosage.

Common sense ought long since to have told us that the doses prescribed in the text-books are only based upon experience in certain cases, or upon experimentation made upon animals. From such data, however, the first author who wrote upon the posology of different substances started, and others have simply copied after the first. If any fact went beyond the well-defined limits, it was wont to be explained by the defective quality or method of preparation of the drug, or by an idiosyncrasy so rare that one would not even take the pains to investigate the matter and see if it were really less rare than had been believed.

Since Heller in 1755 enunciated his philosophical maxims touching the rational method of testing the therapeutic effects of drugs, eminent clinicians have sought to solve the mysteries attending the action of various remedies whose modus operandi remains to this day obscure. Indeed, so great is the diversity of operation pertaining to the commonest remedies, conditioned by the character and circumstances of the case, as well as the amount and quality of the drug, that it is next to impossible to predicate the precise effects of agents whose physiological properties are theoretically and even practically established. The ordinary adult dose of opium, for instance, is 1 gr. (0.06 Gm.); yet in certain diseases, such as peritonitis, ten times that amount may be required to relieve the pain. The doses given in many text-books differ materially from those prescribed in actual practice, being intended to express only the average quantities to be administered, the exact amounts varying with the conditions of the particular case. These conditions may be classed under the heads of age, sex, temperament, idiosyncrasy, habit, state of the system, temperature of the body, time of administration, intervals between doses, cumulative action of the drug, and the contingent considerations of diet, climate, race, etc. - oftentimes a complicated problem even to the most skilful therapeutist. A few suggestions regarding the leading characteristics of dosage, as limited by these various circumstances, may be of value to the student.

The influence exercised by Age is indubitable, as a rule the young requiring smaller doses than adults, the very aged may be also very susceptible. With regard to children several mathematical formulae have been devised, none of which, however, has proved infallible - least of all those based upon adult dosage, itself subject to no little uncertainty. Nor can deductions as to the efficacy of a given dose be drawn from the action of drugs with which the agent is naturally associated. A single drop of laudanum has been known to produce the death of an infant, whereas large doses of belladonna, conium, arsenic, and mercury have been taken with comparative impunity.

The most convenient rule (Young's) adds 12 to the child's age and divides by the age to get a denominator of a fraction whose numerator is 1, this fraction representing the proportion between adult and infant doses. Thus, for a child three years old 3 + 12/3 = 5, or 1/5, the dose being one-fifth of that given to an adult.

Temperament acts as an important agent in modifying the effect of medicinal remedies, phlegmatic subjects readily tolerating certain medicines, such as opium, which those of nervous temperament are unable to bear. Stimuli act upon sanguine patents forcibly, yet upon others their influence may be either tardy or ineffectual. The condition is one which discloses a wide field of inquiry, the mental, moral, and physical tendencies of the individual being involved in the practical administration of medicines.