298 PRINCIPLES OF GENERAL PHYSIOLOGY 



animals in a normal state. The fundamental phenomena of general physiology 

 cannot be discovered by confining our attention to the lower organisms. 



The essential fact in the physiology of sexual reproduction is the advantage 

 gained by the union of the capacities and qualities of two cells from different 

 individuals. Special cells are set apart for this purpose, each being incomplete 

 and incapable of development without the concurrence of the cell of the opposite 

 sex. In the case of the female cell, this incapacity of development is to a certain 

 degree only a relative one. The eggs of some invertebrates can be made to develop 

 by chemical agency and a few rare cases are known where the unfertilised eggs 

 develop into adult animals. 



A short account is given of the facts of heredity as treated on the principles 

 laid down by Mendel. 



In certain cases, plant and animal cells live side by side in the same organism 

 (symbiosis). The plant cells contain chlorophyll and afford carbohydrate material 

 for the animal ; while the cells of the latter appear to provide nitrogenous food 

 for the growth of the plant. 



LITERATURE 



Chemistry. 



General. L. J. Henderson (1913), chapter vi. 

 Proteins. Plimmer (1912, 1913). 

 Carbohydrates. Bunge-Plimmer (1907), chapter viii. 

 Fata. Bunge-Plimmer (1907), chapter vii. 

 Nucle.ins. Walter Jones (1914). 



Growth of Plants. 



Russell (1912). 



Animal Nutrition and Metabolism. 



Lusk (1909). Leathes (1906). Protein Metabolism. Cathcart (1912), 



Reproduction. 



Marshall (1910). 



Mendelism. 



Bateson (1913). 



Symbiosis. 



Keeble (1910). 



