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ELEMENTS OF MATERIA MEDICA.

Cogswell on rabbits ( Experim. Essay on Iodine , 1837), have shewn that,to these animals, iodide of potassium is a powerful poison. It operatesas a local irritant, and thereby inflames the tissues with which it is placedin contact. Four grains injected into the jugular vein of a dog causedconvulsions, and death within a minute. Two drachms introduced intothe stomach gave rise to vomiting and great depression: the latterincreased until death, which occurred on the third day: after deatheccliymosis, ulceration, and redness of the stomach, were observed.(Devergie, op. cit. p. 506.) Dr. Cogswell injected three drachms of theiodide beneath the skin of the back of a dog: the animal died on thethird day : on chemical examination iodine was detected in the bloodfrom the heart, in the brain and spinal cord, the liver, spleen, stomach,muscles, tongue, and the bones freed from their appendages; likewisein the contents of the bladder. (Cogswell, op. cit. p. 91.)

(c.) On man .— Both the physiological effects and therapeutical uses ofiodide of potassium shew that the operation of this salt is analogous tothat of iodine.

The local action of iodide of potassium is that of an irritant. Whentaken internally in large doses it not unfrequently occasions nausea,vomiting, pain and heat of stomach, and purging. Applied to the skinin the form of ointment it sometimes produces slight redness. This saltis much less energetic in its action than free iodine, and, therefore, maybe given in larger doses and continued for a longer period, without evinc-ing the same tendency to produce disorder of the stomach and intestinalcanal. Lugol {Essays, translated by Dr. O’Shaughnessy, p. 65) foundthat baths at 100° F. containing three ounces of iodide of potassium pro-duced temporary itching only ; whereas baths at the same temperaturecontaining ten scruples of iodine caused prickling, then itchiness, smart-ing, rubefaction (which was not commensurate with the itchiness), punc-tuated, separated, or confluent, and subsequently desquamation of theepidermis. The chemical action of iodide of potassium on the tissues isslight, as indeed might be expected, seeing that no obvious changes areproduced when a solution of this salt is mixed with albumen, fibrin, orgelatine, the three most abundant organic constituents of the animalbody.

Iodide of potassium becomes absorbed and is earned out of the systemby the different secretions, in which, as well as in the blood, it may beeasily detected (Buchanan, Med. Gaz. vol.xviii. p. 519; Wallace, Lancet,for 1835-36, vol. ii. p. 6: the latter authority failed to detect it in theblood). Moreover, it deserves especial notice that it has been found inthe urine several days after it has been swallowed. (Christison , Treatiseon Poisons, 3rd ed. p. 185.)

The remote or constitutional effects of iodide of potassium are veryanalogous to those of iodine. Diuresis is a common consequence of itsuse. Relaxation ofbowels is not unfrequent. Occasionally ptyalism hasbeen observed. (Dr. Clendinning, Med. Gaz. vol. xv. p. 869, and Dr.Wallace, Lancet, for 1835 and 36, vol. ii. p. 8.) Dr. Wallace mentionsimtation of throat as being produced by this salt. Atrophy of themamma) is a very rare effect of it, but a case is mentioned by Mr. NesseHill, ( Edinb. Med. and Surg. Journ. vol. xxv. 1826, p.282.) Headache,watchfulness, and other symptoms indicative of the action of this salt onthe nervous system, have been noticed by Dr. Clendinning and Dr.Wallace.