INTRODUCTION 13 



probably plays some part in cell metabolism, may 

 furnish material for building up nucleins, and ac- 

 cording to Faure-Fremiet is concerned in the forma- 

 tion of mitochondria. Cholesterin is considered a 

 waste product of cell life, although it is known to in- 

 hibit haemolysis produced by certain bodies and is 

 thus a protective against toxins, and may have 

 other functions. We should look forward with great 

 interest to the results of investigations that are now 

 being carried on by biochemists, since we depend 

 upon them for an explanation of many of the phe- 

 nomena of life, cellular differentiation, and heredity. 

 We even hope that they may be able to create 

 compounds in the laboratory that we may consider 

 living organisms. However, the task does not 

 seem to be so simple to the biochemist, who should 

 know, as it does to the biologist. Nevertheless, 

 as Jacques Loeb has said, we should "either succeed 

 in producing living matter artificially, or find the 

 reasons why this should be impossible." 



Cell Division. Cells may increase in number by 

 direct (amitotic) or indirect (mitotic or karyokinetic) 

 division. There is no doubt that mitosis occurs, 

 but not all investigators are convinced that cells 

 ever divide amitotically. Direct division was once 

 considered the only method of cell nudtiplication. It 

 was described as a simple division of the nucleus 

 into two parts (Fig. 2), preceded by a division of the 

 nucleolus into two, and succeeded by a constriction 

 of the entire cell ; the result was two daughter cells 

 each with one nucleus containing one-half of the 



