60 PROCEEDINGS OF THE INDIANA ACADEMY OF SCIENCE. 



principally to the latter and was made known in 1838. In 1835 Dujardin 

 had seen living matter in the lower animals and called it sarcode. Schleiden 

 had seen it and called it gum. In 1846, Hugo von jSIohl observed a jelly-like 

 substance in plants and called it protoplasma. It soon dawned upon the scien- 

 tists that the sarcode of the animals and the protoplasma of plants were one 

 and the same thing. In 18G1, Max Schultze fully set forth the protoplasmic 

 doctrine. With this new thought the modern conception of the cell theory 

 would include four thing.s — the cell as a unit of structui'e, the cell as a unit 

 of physiological activitj-, the cell as embracing all hereditarj^ qualities within 

 its substance, and the cell in the liistorical development of the organism. 



The study of the cell is the great field of the biologist. Staining the proto- 

 plasm began in 1868. The centrosome was discovered in 1876, and the 

 chromosomes in 1883. The cliromosomes are noAv regarded as the structural 

 parts which carry the hereditary characteristics. Another problem came up 

 for settlement and that was the origin of the liWng things. From the earliest 

 limes it had been considered that li\ing things were generated spontaneously. 

 In 1836. Franz Schultze performed the first experiments to overthrow the 

 theory of si)ontaneous generation. The death blow to this theory was given 

 ])y Pasteur in 1864 and Tyndall in 1876. It was clearly demonstrated that 

 all life must come from previously existing life. 



The next great advance in biologic thought was the discovery of the 

 germtheory of disease. As early as 1687 when Leeuwenhoek discovered 

 liacteria. some medical men suggested that contagious diseases were due to 

 microscopic organisms that i)a.ssed from the sick to the well. Tiiis suggestion 

 was soon dropjjed and was not re\'i\ed until 1837 when the Italian Bassi 

 demonstrated that the diseases of silkworms were due to the transmission 

 of minute particles from the sick to the healthy. Upon these experiments 

 Henle in 1840 announced the germ-theory of disease. Experimental proof 

 was not found until 1877 when Pasteur and Koch showed that splenic fever 

 of cattle was caused by anthrax germs. 



In 1867, Sir Joseph Lister added another important discovery that of 

 the use of antise])tics in surgery, (^arliolic acid was first used. This has 

 revolutionized surgery. 



In 18,i5», as already stated, Darwin's Origin of Species started on its 

 mission. New interest in evolution was now kindled. Gregor Mendel, in 

 1866 and 1867 announced a great truth — the purity of germ-cells. This, 

 however, attracted little attention on account of Darwin's new thoughts 

 about organic evolution. The truth of Mendel was re-discovered in 1900 

 by the botanist DeVries and others. The names of Galton, Weissmann, 

 Castle and Davenport must be added as important in developing Mendelism 

 as a theory of heredity. The doctrine of evolution is too extensive to review 

 in a Vmef paper. In its establishment as a scientific truth four names should 

 lie Honored l)y being mentioned — those of Lamarck, Darwin, Wallace and 



