CHAPTER XVI. 



ANCIENT AND MODERN VIEWS CONCERNING HETEROGENESIS. 



Organic Morphology. Meaning of Heterogenesis. Views of Aristotle 

 and others. Modified in more Recent Times. Doctrines of 

 Needham and Buffon. Inconsistencies of the latter. Views of 

 O. F. Miiller, Treviranus, and Tiedemann. General Doctrines of 

 M. Pouchet. 



Division of the Subject. Synthetic and Analytic Heterogenesis. Similar 

 differences amongst Fermentations. Origin of 'vital' Forces. 

 Their Mode of Expenditure. Analytic and Synthetic changes 

 during Growth. Influence of pre-existing Protoplasm. Dependence 

 of Life upon Decomposition. Views of Liebig, Freke, and Hinton. 

 Many ' vital ' Processes allied to Fermentations. Natural Ten- 

 dencies to the Formation of ' living ' Matter. Peculiarities of Vital 

 Processes. Distinct though Related Activities in Molecules, Cells, 

 and Organs. Characteristics of Health and Disease. Conditions 

 favourable to the Occurrence of Analytic Heterogenesis. 



THE problems which now demand our attention 

 are somewhat different in nature, though they 

 are not less replete with interest than those which have 

 been hitherto considered. 



It has been proved in the only way in which such 

 a fact could be established, that 'living' matter is 

 formable from its elements, and that the highly com- 



