40 BIOLOGY 



individual started. Figure 15 shows how the single cell divides 

 and continues to divide to produce the many cells of the 

 adult organism. 



2. PROTOPLASM AND THE MECHANICAL THEORY (1861-1885) 



The Discovery of Protoplasm. In 1839 Purkinje first recog- 

 nized under the name "sarcode" the contents of the animal cell; 

 H. Von Mohl in 1846 applied the term protoplasm (Gr. protos = 

 first + plasma = substance or form) to the viscid, granular sub- 

 stance found in plant cells. Cohn in 1850 claimed not only the 

 identity of animal and plant protoplasm but contended that it 

 was the seat of vitality, the basis of life. In 1861 Max Schultze 

 established Cohn's theory and extended the meaning of the 

 word protoplasm to include all living matter. This was a new 

 conception and at once placed the doctrine of biology upon a 

 new basis. If it could be proved that the cell substance, which 

 is the living material in all cells, is always alike, it would show 

 that life could be reduced to one fundamental basis. The name 

 protoplasm had been given to the living substance in the animal 

 embryo and then to a similar material in the cells of plants; but 

 it was Schultze who identified it with the living material of 

 animal cells and extended the name to apply to this universal 

 life substance. With this new conception, he defined a cell as 

 a mass of protoplasm surrounding a nucleus, and thus placed the 

 keystone in the arch of the protoplasmic theories. 



Schultze's conception of protoplasm was somewhat expanded 

 and made more significant by Professor Huxley in 1866. Hux- 

 ley, giving to it the name "physical basis of life," drew far- 

 reaching conclusions as to the significance of the phenomenon 

 that we call life, based upon this universal physical substance. 

 He argued that the properties of life are simply characters of 

 this protoplasmic substance, just as other properties are char- 

 acteristic of water; and that life represents no distinct entity, 

 but is simply a name applied to the combined properties of 

 this remarkable chemical compound, protoplasm. This started 



