l6o LIFE AND DEATH. 



mon element, the cell. Contemporary anatomists, 

 Koelliker, Max Schultze, and Ranvier, have thus 

 established the generality of the cellular constitution, 

 while zoologists and botanists confirm the same law 

 for all animals and vegetables, and exhibit them all 

 as either unicellular or multicellular. 



The Cellular Origin of Complex Beings. — At the 

 same time embryogenic researches showed that all 

 beings spring from a corpuscle of the same type. 

 Going back in the history of their development to the 

 most remote period, we find a cell of very constant 

 constitution — namely, the ovule. This truth may be 

 expressed by changing a word in Harvey's celebrated 

 aphorism — omne vivum ex ovo ; we now say omne 

 vivuni e cellula. The myriads of differentiated ana- 

 tomical elements whose association forms complex 

 beings are the posterity of a cell, of the primordial 

 ovule, unless they are the posterity of another equiva- 

 lent cell. The second task of histology in the latter 

 half of the nineteenth century consisted in following 

 up the filiation of each anatomical element from the 

 cell-egg to its state of complete development. 



The whole cellular theory is contained in the 

 two following statements, which establish the mor- 

 phological unity of living beings : — Everything is a 

 cell, everything comes from an initial cell; the cell 

 being defined as a mass of substance, protoplasm or 

 protoplasms, of an average diameter of a few microns. 



§ 2. The Second Period : the Division of 

 THE Cell. 



Second Period: Constitution of the Cell. — This was, 

 however, only the first phase in the analytical study 



