98 MATERIA MEDICA AND THERAPEUTICS. 



disturbed nutrition as gout and chronic rheumatism. It is 

 possible that arsenic affects the life processes of other living 

 particles in the body besides the tissue elements, namely, the 

 organisms of certain diseases. Thus it is, next to quinine, the 

 most successful medicinal agent in the treatment of chronic 

 malaria, brow-ague, and other varieties of neuralgia due to the 

 same cause, and malarial cachexia ; and is also used with advan- 

 tage in hay-fever. li; sometimes also dispels lymphomatous 

 tumours. Beyond a safe amount, arsenic produces a series of 

 nutritive disorders in the tissues, characterised chiefly by de- 

 bility and nervous disturbances, known as " chronic arsenical 

 poisoning," which need not be detailed here. 



Next to nutrition generally, the nervous system appears to 

 be most influenced by arsenic, which is found abundantly in 

 the grey matter of the cord in poisoning by this metal. Here 

 it acts by diminishing the sensibility and reflex irritability of 

 the centres, as well as of the motor nerves and muscles. Pre- 

 parations of arsenic are useful in chorea, various forms of 

 neuralgia, and spasmodic asthma, especially when malaria or 

 anaemia, or both, may happen to be associated with the neurosis. 

 Like phosphorus, arsenic is said to cause increase of the com- 

 pact tissue of bone at the expense of the medullary tissue, but 

 it is not specially used to produce this effect. In large doses it 

 has a depressing effect on the respiration, circulation, and tem- 

 perature. 



4. REMOTE LOCAL ACTION AND USES. 



Arsenic is excreted chiefly in the urine in the form of 

 arsenious acid; also by the liver and skin. It is not known 

 to affect the kidney specially, but is sometimes used in chronic 

 Bright's disease. The liver, as we have seen, is modified 

 in its activity; and part of the value of arsenic in chronic 

 gout, gravel, and skin diseases, may be referable to its action on 

 the greatest metabolic organ in the body. Either thus indirectly, 

 or directly, its effect on the skin is so remarkable, that it 

 is the most valuable of all internal remedies for certain erup- 

 tions obviously connected with disordered nutrition, such as 

 psoriasis, chronic eczema, acne, and pemphigus, whilst it aggra- 

 vates such diseases as erythema multiforme. Donovan's Solu- 

 tion is used in syphilides. 



5. METHODS OF ADMINISTERING ARSENIC, AND PRECAUTIONS 



IN ITS USE. 



Arsenical preparations should always be given immediately 

 at the end of meals, unless their gastric effect be desired, which 

 is rarely the case ; and they ought not to come in contact 



