558 LORANDE LOSS WOODRUFF 



fically toxic to themselves and which form an unfavorable medium 

 for the continued growth of a succession of the same species.^ 

 Recent work on various species of bacteria and molds points in 

 the same direction. Eijkman,'^ for example, observed that these 

 forms growing on artificial nutrient media form waste products 

 which inhibit growth and also that these products of a given 

 species are, as a rule, more toxic to that and closely related spe- 

 cies than to those more distantly related. Further, Kuester^ 

 noted that molds grown in a solution produce substances which 

 inhibit the growth of further inoculations. 



Considerable experimental work on various vertebrates has 

 demonstrated that fatigue is due to the accumulation of met- 

 abolic products. Ranke, and later Mosso^ observed that the 

 blood of fatigued animals when injected into the circulation of 

 fresh ones brought about all the symptoms characteristic of fa- 

 tigue, and Weichart^ was able to isolate a toxin from fatigued 

 muscle which, when injected into animals, gave rise to similar 

 conditions. 



Semper^ in 1874 made a series of experiments with snails, in 

 which he found, for example, that snails bred singly in two liters 

 of water attained to more than three times the size of those grown 

 in groups of twenty in the same amount of water. In all the ex- 

 periments the amount of available food was maintained at the 

 optimum. In other experiments the number of snails was con- 

 stant and the volumes of water unequal, and the same result 

 was obtained. Semper concluded that the results were in some 



* Cf. Schreiner and Sullivan, Journ. Biol. Cbem., vol. 6, pp. 39-50, 1906, and 

 later papers; also Cameron, Journ. Phys. Chem., vol. 14, p. 425, 1910, and U. S. 

 Farmers' Bull., 257, 1906. 



^Eijkman, Centralbl. f. Bakt. 1, 37, p. 436, 1904. Cf. also Rahn, Centralbl. f. 

 Bakt. 2, 16, p. 417, 1906. 

 5 Kuester, Ber. d. d. Bot. Gesell., Bd. 26a, p. 246, 1908. 



* Ranke, Tetanus: Eine physiologische Studie. Leipzig, 1865. Mosso, Arch. f. 

 Anat. u. Physiol., Physiol. Abth., p. 89, 1890. 



MVeichart, Munch Med. Wochenschr., Bd.f 2, p. 2121, 1904. 



^ Cf. Lee, Journ. Amer. Med. Assn., vol. 46, 1906, and Slade, Journ. Physiol., 

 35, 1907. 



^ Semper, Arb. a.d. Zool-Zoot. Inst., Wurzburg, Bd., 1, 1874. Animal life, pp. 

 159-167, 1879. 



