372 MATERIA MEDIC A AND THERAPEUTICS. 



Litmus. A blue pigment prepared from various 

 species of Roccella. 



Characters. Small blue lumps, readily reduced to powder. 

 Preparations. 



1. Tincture of Litmus. 1 in 10. 



2. Blue Litmus Paper. 



3. Red Litmus Paper. 



USE. 

 Litmus is employed only in chemical testing. 



Cerevisise Fermentum BEER YEAST. The 

 ferment obtained in brewing beer. 



Characters. Viscid, semi-fluid, frothy, exhibiting under the 

 microscope numerous round or oval confervoid cells. 

 Dose. One to two table-spoonfuls. 



Preparation. 



Cataplasma Fermenti. Yeast Poultice. Yeast, 6 ; Flour, 14 ; 

 Water (at 1008), 6. The mass to be placed near the fire 

 till it rises. 



ACTION AND USES. 



Yeast poultice is believed to act as a sedative and anti- 

 septic, and was formerly applied to sloughing sores, ulcers, and 

 boils. Its value is very questionable. 



Yeast has also been given internally on theoretical grounds 

 in zymotic diseases and in diabetes, but probably without 

 success. 



FUNGI. 



MuscarisB Nitras. (M>$ Officinal.) Nitrate of 

 Muscarin, the liquid alkaloid of Agaricus muscarius 

 or Amanita muscaria, the Fly Agaric. 



Dose. sV to \ gr. 



ACTION AND USES. 



The action of muscaria is almost exactly opposed to that of 

 atropia in every respect, except that it dilates the pupil when 

 applied locally. It also contracts the pulmonary vessels. It 

 has been used as an anhidrotic. 



