62 PHYSIOLOGY CHAP. 



pensable to life. Some animals have adapted themselves to a 

 purely protein diet, and, further, to a single form of the same. 

 Thus, e.g., the clothes-moth lives exclusively on the keratin of 

 which the hairs of the wool or fur consist, and from which it 

 derives all that is necessary for the construction of its protoplasm. 

 Again, as we shall see, it is possible to keep a dog alive, and in its 

 normal state, on a purely flesh diet, while this is found impossible 

 on an exclusive diet of fats and carbohydrates, no matter how 

 abundant. 



The chief part of the mineral substances which enter into the 

 chemical composition of animals cannot be assimilated as such, but 

 only when they are present in organic combinations, as, e.g., the 

 calcium phosphate of milk casein, the potassium salts of muscle 

 protein. If mice are fed on casein from which the greater part of 

 the salts contained in the organic combinations of milk have been 

 previously washed out, and if sugar be added, as well as all the 

 salts contained in the ashes of milk in a non-organic form, the 

 mice perish slowly during this diet, and succumb after about forty 

 -days (Lunin). This and similar experiments on artificial feeding 

 in other animals, show that they are only capable to a small 

 extent of assimilating inorganic substances, i.e. of binding them 

 synthetically into the protein molecule on which the living 

 protoplasm is nourished. 



BIBLIOGRAPHY 



The following may be consulted for the literature of the Theory of Evolution : 

 LAMARCK. Philosophic zoologique. Paris, 1809. 

 CHARLES DARWIN. On the Origin of Species by Means of Natural Selection. 



London, 1859. 



C. VON NAGELI. Mechanisch-physiologische Theorie der Abstammungslehre. 1884. 

 WEISMANN. Das Keimplasme : eine Theorie d. Vererbung. Jena, 1892. 

 H. DE VRIES. Die Mutationstheorie. Leipzig, 1901, 1903. 

 YVES DELAGE. L'Heredite et les grands problemes de la biologic geuerale Paris 



1903. 



DETTO. Die Theorie d. direkten Anpassung. Jena, 1904. 

 PAULY. Darwinismus und Lamarckismus. Munich, 1905. 

 LOTSY. Vorlesungen iiber Deszendenztheorien. Jena, 1906. 

 SCHNEIDER. Einfiihrung in die Deszendenztheorie. Jena, 1 906. 

 RIGNANO. Sur la transmissibilite des caracteres acquis. Paris, 1906. 



The two following text-books may be consulted for the general physiology of 

 plants, and their characteristics as distinct from animals : 



E. STRASBURGER, F. NOLL, H. SCHENCK, A. F. W. SCHIMPER. Lehrbuch d 



Botauik. Jena. G. Fischer, 5th ed., 1902. 



W. PFEFFER. Lehrbuch d. Pflanzenphysiologie. Leipzig, 1897-1901. 

 Recent English Literature of the subject : 



W. PFEFFER. The Nature and Significance of Functional Metabolism in the Plant. 



Proc. Roy. Soc., London, 1898, Ixiii. 93. 

 K. PEARSON. Data for the Problem of Evolution in Man. Proc. Roy. Soc. London 



1900, Ixvi. 23, 316. 

 K. PEARSON. Mathematical Contributions to the Theory of Evolution. Proc. Roy. 



Soc., London, 1900, Ixvi. 140. 



