18 GENERAL PROPERTIES OF LIVING MATTER. 



to me the most probable one, inasmuch as it tries to explain why 

 certain properties of ancestors, even in the second or third 

 generation, may re-appear ; why bodily and mental peculiarities 

 are directly transmitted from parents and grandparents to their 

 offspring. With this theory, which suggests a direct increase 

 of plastidules within a limited bulk of living matter, we may 

 readily understand why, with progressive development of a 

 species, a perfection takes place which leads to the production of 

 more and more advanced beings from relatively lower ancestors. 

 HaeckeFs view can scarcely be supported so long as we know 

 that a change of motion as function is always due to a material 

 cause, namely, change of molecules in quality and quantity. All 

 this is speculation only, though entirely legitimate as an attempt 

 to bridge over precipices which present insurmountable obstacles 

 to the passage of our intellect. 



Historical /Sketch of the Study of Living Matter. In 1835, 

 Dujardin discovered a contractile substance common to low 

 animals, which he termed " sarcode," but he was far from the 

 knowledge that this substance exists in all animals, believing it 

 to be peculiar to the lowest forms. After Schleiden, of Jena, in 

 1838, discovered the form-elements of plants, and proposed for 

 them the name of " cells," Theodor Schwann, of Berlin, in 1839, 

 found a striking analogy between the intimate structure of 

 vegetable and animal organisms, and asserted that the " cells " 

 are the simplest constituent parts of all tissues of the animal 

 body as well as of the plant. In his opinion, each cell is a 

 vesicle composed of a transparent membrane, containing a 

 fluid in which is suspended a central solid body, the nucleus. 

 Schwann believed that cells may originate in a substance, the 

 plasma, independently of former cells, and through the authority 

 of Johannes Muller, who fully accepted Schwann's doctrine, this 

 became the leading one, so that even C. Rokitansky held at first 

 that the plasma of the blood may, under favorable circum- 

 stances, produce cells. It was the discovery of Rudolph Vir- 

 chow, in 1852, that the cells are really the seats of life, and that 

 every cell must originate from a former cell : Omnis cellula e 

 cellula. Virchow, however, adhered to Schwann's original idea 

 as to the construction of cells, although a very simple considera- 

 tion will show that this cannot be correct viz., the consideration 

 of the fact that no living material is ever a fluid, but always 

 either a solid or a jelly-like, semi-fluid substance. The next 

 who advanced the cell-theory was Max Schultze, of Bonn. He 



