KEY AND INDEX 



Cavendish, Priestley, Scheele, and Lavoisier), whose efforts laid 

 the foundation for all modern knowledge of the gases about the 

 close of the eighteenth century. For an account of their work, 

 see "The Beginnings of Modern Chemistry," Vol. IV, p. n. 



Amoeba. A protozoan, which is present almost everywhere 

 in fresh water, and in moist earth, and is usually taken as a 

 type of unicellular animals. Certain forms of the Amoeba pro- 

 duce diseases, such as dysentery and abscess of the liver. 

 Microscopic organisms were studied by such early microscopists 

 as Leeuwenhoek (see Vol. II, p. 179) and Robert Hooke (see 

 Vol. II, p. 217), but it remained for investigators of the nine- 

 teenth century to demonstrate their importance. See "Parasitic 

 Diseases," Vol. IV, p. 204. 



Anaesthetic. An agent used to produce loss or impairment 

 of sensibility. The word was coined by Dr. Oliver Wendell 

 Holmes. The use of ether, the most important general anaes- 

 thetic known, was discovered by Dr. W. T. G. Morton, a dentist, 

 in 1842. The anaesthetic property of chloroform was discovered 

 by Sir. J. Y. Simpson, of Edinburgh, in 1843. See "Painless 

 Surgery," Vol. IV, p. 208. 



Anastomosis. In anatomy, the joining of branches of a vessel 

 with other vessels or branches. Hunter's discovery of the func- 

 tion of this anastomosis in arteries and veins marked an epoch 

 in surgery. See Vol. IV, p. 82. 



Aneurism. A disease (or injury) of the walls of an artery re- 

 sulting in the formation of a pulsating tumor or sac. The Eng- 

 lish surgeon, John Hunter, about 1770, devised an operation for 

 the cure of this condition, his discovery being the direct result 

 of an operation performed on a deer in Richmond Park. See 

 "Hunter's Operation for the Cure of Aneurism," Vol. IV, p. 81. 



Aniline. An organic substance, with the formula QHjN H 2 . 

 It was discovered in 1826, but was of no commercial importance 

 until 1856, when W. H. Perkin prepared a purple dye from it. 

 See "Coal-tar Colors," Vol. VIII, p. 311. 



Animism. A system of philosophy introduced by Stahl, based 

 on the idea that the soul is the seat of life. See "Eighteenth 

 Century Medicine," Vol. IV, p. 185. 



Annealing. A process for increasing the ductility of metals 

 and glass. The usual method of annealing is by heating and then 

 cooling slowly. 



Anode. The electrode at which a current of positive electricity 

 enters a battery. The other electrode is called the "cathode." 



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