pound of which they form part, the action can be ascribed with certainty to the other ion, unless the change arises from alteration of the physical properties of the fluids. Thus, the sodium ion and the chloride ion have been ascertained to be both practically inert, except in so far as they change the osmotic pressure; hence if a sodium salt or a chloride be found to cause some change which is not due to the physical alteration, the action is to be attributed to the other ion of the molecule. Many observations point to the conclusion that the irritability of muscle and nerve depend upon the presence in them of compounds of proteid with the various ions, sodium, potassium and calcium, in definite proportion. Furthermore, it has been demonstrated that the physiological effects of certain drugs can be modified in definite ways by the addition of chosen radicals to the molecule. Thus, the convulsive action of strychnine on the spinal cord is changed to a paralyzing effect by the introduction of methyl into the molecule. Again, the introduction of chlorine ions into certain fatty molecules increases their narcotic and toxic properties. The results of these investigations would seem to afford ground for the opinion that in the forces of ionic attraction and repulsion is to be found the explanation of the rouleau formation of red blood-corpuscles, the agglutination of bacteria in appropriate media, and the obscure facts of chemotaxis, illustrated by the attraction or repulsion which certain chemical media have for some bacteria and for leucocytes. Protoplasmic movements doubtless take place by means of ions, the electricity-bearing portions breaking down when in solution, and it has been suggested that toxic and antitoxic effects may be due to various alterations in the composition of protoplasm forming living tissue. If a toxin which depends for its activity on a large number of monovalent anions can be controlled by a small number of bivalent anions, or even ions of much higher valence (thus requiring a smaller quantity), the question of remedy is apparent. So, among antiseptics, salicylic acid may be destructive to low forms of life because it is easily dissociated in the tissue electrolytes and liberates large numbers of poisonous hydrogen kations. Mercuric bichloride and copper kations are for the same reason effective, but the solution of a mercury salt in strong alcohol (a substance in which no electrolytic dissociation occurs) has no germicidal properties. The neutralization of the toxic effects of phenol by concentrated alcohol is susceptible of a similar explanation. Under ordinary conditions, ions of high valence are markedly disinfectant; those of lower valence less so. As regards mercury salts, dissociation may be retarded by the introduction into and aqueous solution of either alcohol or of another salt dissociating the same anions. For example, calomel treated with increasing proportions of sodium chloride shows a steady decrease of toxicity, the cause of which is the progressive suppression of the formation of mercury ions. The dissociating power of a solvent is believed to be a function of all the physical or chemical properties of a substance, and not of any one of them. The results of experiment tend to demonstrate the chemical inertness of molecules. As the reactions proceed, and the ions already present are used up, it is found that the molecules are gradually dissociated and furnish new ions, which then enter into the reaction. The chemistry of atoms and molecules has thus given place to the chemistry of ions. Osmotic Pressure is defined as the resistance offered by a non-permeating salt to the passage through a partially permeable membrane of the fluid in which it is dissolved; and this varies with the number of molecules and ions. For the occurrence of osmotic interchange the separating membrane must be permeable to water, but impermeable to substances dissolved in it; and the capillary wall, which separates the blood from the lymph, is not of this character, since through it there may take place both filtration due to difference of hydrostatic pressure and diffusion of substances in solution. The laws of osmosis may be thus summarized: (1) Solutions separated by any membrane permeable to water tend to have an identical molecular composition. (2) If the membrane is perfectly permeable to both solvent and dissolved substance the exchange of molecules will take place without change in pressure or volume. (3) If the membrane is less permeable to the dissolved substance than to the solvent, an increase of of liquid, or increase of tension, will occur in the stronger solution. (4) If a membrane is differently permeable to one dissolved substance than to another, equimolecular solutions of the less diffusible substance will be hyperisatonic (hypertonic) to the more diffusible. In the interchange of bodily fluids, however, the forces of filtration and diffusion complicate those of osmosis in the transference of material. The classification of drugs, which is adopted here, is one in accordance with the parts on which they principally act. DIVISION I.-DRUGS ACTING UPON ORGANISMS WHICH INFECT THE HUMAN BODY, OR UPON PROCESSES GOING ON OUTSIDE IT A. Antiseptics are drugs which prevent the growth of microorganisms, destroy or render innocuous the toxic products of their action upon the tissues of the body, or interfere with the absorption of such products. By some the use of the word antiseptic is limited to those substances which restrain the development of microorganisms, while those which destroy the vitality of the latter are designated as germicides or disinfectants. The term disinfectant, by extension, is applied to those agents which kill non-pathogenic bacteria, as well as to those which destroy disease germs. Much discrepancy of statement is to be found regarding the fact of certain drugs being really antiseptics and as to the relative power of various antiseptics, owing to the circumstance that antiseptics act differently upon different organisms, while the difference between inhibiting the growth of micro-organisms and destroying their vitality has been lost sight of. There are also certain factors determining the efficiency of an antiseptic which should be taken into consideration. Among these are the following: The nature of the antiseptic agent, the strength in which it is used, the temperature at which it acts, the nature and number of the micro-organisms, the nature and quantity of the associated material, and the time of exposure. In testing the value of any antiseptic it is requisite that all instruments and substances employed in the procedure should first be exposed to a temperature sufficient to destroy any adventitious bacteria. A cultivating medium, such as agar jelly, having been placed in two test-tubes, the substance to be tested, in suitable solution, is added to one of them; after which some fluid containing the micro-organisms selected is poured into both the tubes. Both are then closed with sterilized cotton to prevent the entrance of germs from the air, and observation from time to time will show how far the development of the micro-organisms has been interfered with by the supposed antiseptic. As the potency of an antiseptic is dependent upon so many circumstances, it is impossible to determine with exactness the relative efficiency of various agents. In the following list the most powerful and generally used antiseptics are placed first. 1. Heat is the best antiseptic, but there must be a temperature of at least 100°C. (212°F.). Infected clothing, bedding, etc., may be heated in a dry-air chamber.to between 93.5° and 149°C. (200° and 300°F.), but, on account of its superior penetrating qualities, steam, driven, under pressure, through the articles is decidedly preferable. Instead of this, the infected material may be boiled in water. Surgical instruments are generally disinfected in this way, but I per cent. of washing soda (sodium carbonate) should be added to the water to prevent their rusting. 2. Corrosive Mercuric Chloride in a solution of 1 in 1000 is commonly used for disinfecting the hands and is sometimes employed in surgery and obstetrics. For most uses, however, one part to 3000 or 5000 of water, or even weaker, is the limit of safety. Gauze of the strength of 1 to 2000 will blister, if the skin is damp. 3. Formaldehyde, the official solution of which contains not less than 37 per cent., by weight, has extraordinary power as a surface disinfectant. It is especially useful for the disinfection of rooms and their contents when volatilized from a specially constructed lamp. 4. Chlorine for most purposes is too irritating, but the gas (which is generated by the action of hydrochloric acid on potassium chlorate or manganese dioxide) may be used to disinfect rooms. It is open to the objection that it attacks and bleaches many substances. 5. Chlorinated Lime is the best antiseptic for all excreta. 6. Phenol, or Carbolic Acid, is used but infrequently. If surgical instruments have been previ ously sterilized, the use of phenol indicates a distrust, on the part of the surgeon, of his assitants. 7. Various Cresol compounds are powerful antiseptics and employed to a large extent. 8. Bromine, and, 9, Iodine, are rarely used, because they are too irritating. 10. Iodoform is used for dusting upon wounds, sores, etc., but is objectionable on account of its extremely disagreeable odor. It should be previously sterilized. 11. Quinine, and, 12, Salicylic Acid, are too expensive for ordinary use. 13. Boric acid is used for many surgical purposes. Since in about a 21⁄2 per cent. solution it inhibits the growth of most bacilli, it may be employed to preserve solutions intended for hypodermatic use. 14. Zinc chloride, and, 15, Potassium Permanganate, are much used for domestic purposes. 16. Solution of Hydrogen Dioxide is the principal ingredient of various popular disinfectants. 17. Sulphurous Acid, generated by the burning of sulphur, is used to disinfect rooms. It should always be associated with moisture. 18. Charcoal is not a disinfectant, but merely a deodorizer. 19. Cresote, Zinc Sulphate, Ferric Oxide, Methylene Blue, Alcohol and Balsam of Tolu are not much used. Internal antisepsis has for many years been in dispute. The objection has often been raised that there are no known drugs which when swallowed or inhaled, with certainty will destroy micro-organisms, either in the gastro-intestinal tract or respiratory passages, unless they are sufficiently concentrated to injure or prove fatal to the patient. By some, however, it is claimed that calomel, betanaphthol and some other agents are capable of destroying certain varieties of micro-organisms in the stomach and intestines; and, whether this is true. or not, it is undoubtedly a fact (and one that is often lost sight of) that an infinitely small amount of a remedy which could not be administered in sufficient amounts to destroy, will often completely inhibit the growth of micro-organisms. Such drugs should therefore be classed as internal antiseptics. Antizymotics are agents which arrest fermentation, and are sometimes divided into two groups, antiseptics and disinfectants. The fermentative processes may be caused by organized ferments, such as bacteria and the yeast-plant, or by unorganized ferments (enzymes), such as pepsin, pancreatin, diastase, ptyalin, etc. Deodorants, or deodorizers, are substances which destroy foul smells. The volatile deodorants are mainly oxidizing and deoxidizing substances which act chemically on the noxious effluvia, while the non-volatile deodorants are mainly absorbents, which condense and decompose them. Many antiseptics and disinfectants are also deodorants. B. Anthelmintics are agents which kill (vermicides) or expel (vermifuges) parasitic worms infesting the alimentary canal. Four kinds of these parasites are commonly met with: (1) Tape-worm (Tania solium and Tania mediocanellata). Anthelmintics: Aspidium (mostly used), Granatum, Pelletierine Tannate (easily administered and very efficient), and Pepo. (2) Round-worm (Ascaris lumbricoides). Anthelmintics: Santonin, Oil of Chenopodium, and Spigelia. Anthelmintics for the tape- or round-worm should be given when the alimentary tract is empty, to ensure their coming into contact with the parasite, and a purgative should precede the anthelmintic by a few hours. If the latter is itself not also a cathartic, another dose of purgative medicine should be administered after it, to bring away the worm or worms. When aspidium is employed castor oil should always be avoided, as its use is attended with considerable danger. In the instance of tape-worm, in order to determine whether the head is discharged, each stool should be received into a separate vessel, then mixed with water, and filtered through coarse muslin. (3) Thread-worm (Oxyuris vermicularis). Anthelmintics: Rectal injections of salt water, infusion of quassia, calumba or nutgall, solutions of iron salts, or diluted oil of turpentine are commonly recommended. Large soap and water enemata, the patient being in the knee-chest position, give the best results. Lime water is often very efficient. In the instance of children it is advised that the lower bowel should be first emptied by an injection of warm soap and water. The child should then be placed upon a bed with its buttocks elevated, and the tube of the syringe be passed gently within the inner sphincter. The fluid (soap and water, lime water, or salt and water), previously warmed, must be injected with some little force, so that it may be lodged in the upper part of the rectum; otherwise expulsive efforts will be immediately excited. It is best that the enema should be given at bedtime in order that it may be retained for a sufficient length of time. (4) Hook-worm (Anchylostomum duodenale and Uncinaria americana). Anthelmintics: Thymol, 1 gm. (15 gr.), per day is taken. In severe instances this treatment may be preceded by a few doses of Betanaphthol. C. Antiparasitics or parasiticides are substances which destroy parasites. The term is usually applied to those which are destructive to the animal and vegetable parasites found upon the cutaneous surface but of late has been extended to cover those found within the body as well. (1) For the various forms of tinea the following are used: Mercurial preparations, especially the oleate, tincture of iodine, glycerite of phenol, an ointment of pyrogallic acid, a boric acid or salicylic acid lotion, sulphurous acid, formaldehyde and thymol; and if the patches are small, severe irritants, as croton oil, |