94 MATERIA MEDICA AND THERAPEUTICS. 



2. Pel-chloride of Mercury. This is the most powerful o! 

 all mercurials. It is one of the most active of antiseptics, being 

 100 times as strong as carbolic acid, and may be used to dis- 

 infect foul ulcers, especially of syphilitic origin, a certain 

 amount of caustic and stimulant effect being secured at the 

 same time. It must be cautiously employed. It is also used 

 to destroy the fungus of ringworm. Internally, as the Liquor 

 (a weak solution) , it is given in syphilis only, never as a purga- 

 tive. In this form, the perchloride is by no means an irritant 

 preparation of mercury, but rather the reverse. Lotio Hy- 

 drargyri Flava, " yellow wash," containing the yellow oxide, is 

 applied to syphilitic sores. 



3. Subchloride of Mercury. Calomel resembles metallic 

 mercury in being used externally and internally, as a purgative, 

 alterative, and antisyphilitic remedy. Externally it is applied 

 to syphilitic sores and chronic inflammatory growths as calomel 

 dust, by fumigation, as the unguentum, and as the black wash. 

 Internally calomel is a valuable purgative, with the powerful 

 action as an indirect cholagogue and hepatic stimulant already 

 described. The compound calomel pill (Plummer's pill) is in 

 much repute as a hepatic stimulant and alterative, with little or 

 no directly purgative effect, given every night or every other 

 night for a week at a time, in gout and loaded conditions of the 

 system consequent on free living. Calomel, combined with 

 opium, was the favourite mercurial employed by the last 

 generation of surgeons and physicians in the treatment of 

 inflammation, to which we have already referred. In syphilis 

 the same combination is still employed with success. 



4. The Oxides, Iodides, and Ammonio-Chloride of Mercury. 

 These substances, although forming a convenient group, 

 belong, as regard their action and uses, partly to the second and 

 partly to the third group above. Thus the following closely 

 resemble the perchloride, viz. llydraryyri < >xidum Flavum, Hy- 

 dra r^yri Oxidum Rubrum, Hydrargyri lodidum Rubrum, and 

 Hydrargyrum Ammoniatum. The first two are almost exclu- 

 sively used in syphilis, and externally, cliiclly according to the 

 opinion and custom of the practitioner. The " white precipitate" 

 ointment is useful as a parasiticide, and as a stimulant applica- 

 tion to chronic inflammatory eruptions of almost any kind in 

 ehildrt >n. Along with the Subchloride is to be classed Hydrargyri 

 lodidum Yiride, which is much used in syphilis by some sur- 

 geons. Donovan's Solution is valuable in obstinate syphilides. 

 The student will not forget that the Lotio Hydrargyri Flava 

 really contains the yellow oxide, and the Lotio Hydrargyri 

 Niin'a, the black oxide, although they are reckoned as pre- 

 parations of the perchloride and Subchloride respectively. 



