70 MATERIA MEDICA AND THERAPEUTICS. 



healing is associated. A solution of this salt is the basis of the 

 ordinary .'.'red lotion" of many hospital pharmacopoeias; and 

 other weak solutions of the same may be employed as 

 a wash or injection for the eyes, urethra, vagina, and other 

 accessible mucous tracts. The oxide and carbonate of zinc, 

 and calamine, act locally as mild astringents in inflamed con- 

 ditions of the superficial layers of the skin, such as eczema, 

 controlling exudation and hypersemia, and protecting the parts 

 from the air. Being insoluble in water, they are applied in the 

 form either of powder or of the ointment. 



Internally, the local action of zinc corresponds. It is but 

 little used in the mouth or throat, but its effect on the stomach 

 as a local irritant furnishes us with the most familiar of our 

 direct emetics. Sulphate of zinc, in doses of 20 grains, causes 

 rapid and complete vomiting, attended by less immediate de- 

 pression and less subsequent nausea than antimony and 

 ipecacuan. It is much employed in narcotic poisoning ; more 

 rarely in croup, diphtheria, and phthisis, to clear the air pas- 

 sages ; or even to empty the stomach in painful dyspepsia. The 

 oxide on reaching the stomach is dissolved, and acts like the 

 soluble salts of zinc. 



In the intestine the irritant action of zinc is continued, if 

 it be given in large doses, but this effect is never desired thera- 

 peutically. On the contrary, the oxide, in sufficient doses to 

 relieve a moderate superficial catarrh, is often a very efficacious 

 astringent in the treatment of diarrhcea in children. 



2. ACTION IN THE BLOOD. 



Zinc readily enters the circulation, but nothing is known 

 respecting its influence on the plasma or corpuscles which can 

 be turned to therapeutical account. 



3. SPECIFIC ACTION AND USES. 



The action of zinc upon the tissues has been learned chiefly 

 from its effect in certain diseased conditions in man, and is but 

 imperfectly understood. It appears to bo a depressant to the 

 nervous and muscular systems, and has been employed with un- 

 questionable success in epilepsy, chorea, and whooping cough, 

 all of which are characterised by nervo -muscular excitement. 

 Observations on animals, in which the irritability of the volun- 

 tary and cardiac muscles is found to be decidedly reduced by 

 zinc, confirm this experience. 



4. REMOTE LOCAL ACTION AND USES. 



The kidneys and mammary gland, and probably the mucous 

 surfaces and skin, are the channels of elimination of zinc. It 



