CONTENTS xvii 



PAGE 



in 1668, puts the question to experimental test and overthrows 

 the belief in the spontaneous origin of forms visible to the un- 

 aided eye, 279. The problem narrowed to the origin of micro- 

 scopic animalcula, 281. Needham and Buffon test the ques- 

 tion by the use of tightly corked vials containing boiled or- 

 ganic solutions, 281. Microscopic life appears in their infusions, 

 282. Spallanzani, in 1775, uses hermetically sealed glass flasks 

 and gets opposite results, 282. The discovery of oxygen raises 

 another question : Does prolonged heat change its vitalizing prop- 

 erties? 284. Experiments of Schwann and Schulze, 1836-37, 

 284. The question of the spontaneous origin of microscopic life 

 regarded as disproved, 286. III. Pouchet reopens the question 

 in 1858, maintaining that he finds microscopic life produced in 

 sterilized and hermetically sealed solutions, 286. The question 

 put to rest by the brilliant researches of Pasteur and of Tyndall, 

 288, 289. Description of Tyndall's apparatus and his use of op- 

 tically pure air, 290. Weismann's theoretical speculations re- 

 garding the origin of biophors, 292. The germ-theory of disease, 

 293-304. The idea of contagium vivum revived in 1840, 293. 

 Work of Bassi, 294. Demonstration, in 1877, of the actual con- 

 nection between anthrax and splenic fever, 294. Veneration of 

 Pasteur, 294. His personal qualities, 296. Filial devotion, 297. 

 Steps in his intellectual development, 298. His investigation of 

 diseases of wine (1868), 299. Of the silk-worm plague (1865-68), 

 299. His studies on the cause and prevention of disease con- 

 stitute his chief service to humanity, 299. Establishment of the 

 Pasteur Institute in Paris, 299. Recent developments, 300. 

 Robert Koch; his services in discovering many bacteria of dis- 

 ease, 300. Sir Joseph Lister and antiseptic surgery, 302. Bac- 

 teria in their relation to agriculture, soil inoculation, etc., 303. 

 Knowledge of bacteria as related to the growth of general biol- 

 ogy, 3°4- 



CHAPTER XIV 



Heredity and Germinal Continuity — Mendel. Galton. Weis- 

 mann, 306 



The hereditary substance and the bearers of heredity, 306. The 

 nature of inheritance, 306. Darwin's theory of pangenesis, 307. 

 The theory of pangens replaced by that of germinal continuity, 

 308. Exposition of the theory of germinal continuity, 309. The 

 law of cell-succession, 309. Omnis cellula e cellula, 310. The 

 continuity of hereditary substance, 310. Early writers, 311. 



