172 INORGANIC AGENTS 



Action of Arsenical Compounds. 



External. — Arsenous acid is a slowly acting caustic on raw surfaces 

 and mucous membranes. It produces considerable pain, and may cause 

 fatty degeneration of the epithelium of the skin, with inflammation of the 

 tissues beneath, and lead to poisoning. In frogs poisoned by arsenic the 

 epidermis peels off very rapidly, owing to degeneration of its lower layers. 

 It is antiseptic and the chief preservative agent in embalming fluids, and 

 is used to kill the protozoan spirochaeta of syphilis and of Vincent's 

 angina and stomatitis. 



In small doses arsenic increases subcutaneous fat and causes the 

 coat of hair in animals to become thicker and more glossy. 



Internal. — Digestive Tract. — In large amounts, arsenic is an irritant, 

 causing loss of appetite, nausea, diarrhea and digestive disturbance. 

 Similar digestive disorders occur after large hypodermatic doses of ar- 

 senic and are due to increased permeability of the capillaries in the walls 

 of the gut, with edema of the bowel, and degeneration and exfoliation of 

 its mucous membrane. In toxic doses arsenic produces gastro-enteritis. 



Blood. — Arsenic is absorbed into the blood, and in some forms of 

 anemia increases notably the number of red corpuscles, and to some extent 

 the hemoglobin. Experimentally arsenic increases the formation of leuko- 

 cytes in bone marrow, and the white cells in the blood, and does not 

 increase the red cells or hemoglobin. It lessens the number of white 

 cells in leukemia. 



Circulation. — It is said that arsenic stimulates the pulse rate when 

 given in minute doses. In large doses it has a local depressing action on 

 the heart — and probably on the vasomotor centre — lowering the force 

 and frequency of the heart and reducing blood pressure. The nerve 

 endings, ganglia, and muscle of the heart are alike paralyzed, and this 

 action takes place when the heart is removed from the body. Arsenic 

 enhances capillary permeability, hence the edema of the skin (puiHness 

 of eyelids), and digestive tract in poisoning. 



Respiration. — In small doses arsenic quickens the breathing and 

 stimulates the respiratory centre; whereas in lethal amounts the respira- 

 tion fails through lowered blood pressure and exhaustion. 



Nervous System. — The nervous apparatus is powerfully influenced 

 by arsenic. Toxic doses cause paralysis of the spinal tracts, in frogs, 

 with loss of sensation, motion, and reflex action, and the brain and nerves 

 are also depressed. The nerve trunks are chiefly affected in the higher 

 animals. There is peripheral neuritis and trophic changes occur. Medici- 

 nal doses of arsenic are stimulant to the nervops system generally. 



Bone. — Experimentally arsenic has been found to increase the den- 

 sity of bone in growing animals of poor nutrition, the cancellous tissue 

 being transformed to a certain extent into hard bone — possibly by in- 

 crease of vascularity in the bone marrow. 



Metabolism. — Therapeutic doses probably diminish tissue change 

 and the elimination of urea. Continued dosage diminishes liver activity 

 and glycogen formation, thus more nitrogen is eliminated as uric acid and 



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