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IOWA ACADEMY OF SCIENCE Voi.. XXVII, 1920 
appear. But on the other hand when the muscle was not sub- 
jected to such low temperatures ( — 4°C. to — 5°C.) in the first 
period and then was non-irritable for several changes in the range 
of temperature (about five) a third maximum appeared between 
the first and last. 
The relative positions of the maxima contractions as I have 
found them in twenty experiments are as follows: The first 
maxima falls in the first period between — 1° and — 3°C. ; the 
second maxima fall^ between — 2° and — 3°C. of the second 
period ; the third maxima falls between 36° and 40° C. of the third 
period; while that of rigor caloris is usually between 48° and 
50° C. of the fourth period. 
REFERENCES 
1. W. H. Howell, Text-Book of Physiology, p. 30-31, 1919. 
2. Vincent and Lewis, Journ. Physiol., vol. 26, p. 445, 1901. 
3. E. B. Meigs, Amer. Journ. Physiol., vol. 24, pp. 13 and 184, 1909. 
4. Vrooman, Biochemi. Journ., vol. 2, p. 363, 1907. 
5. C. L. Edwards, Biol. Lab. Studies, Johns Hopkins Univ., vol. 4, p. 
32, 1887. 
6. Gadow, Cambridge Nat. Hist., p. 58, 1901. 
7. Miss M. C. Dickerson, The Frog Book, p. 16, 1908. 
8. Maurel et Lagriffe, Compt, rend, soc. biol., vol. 52, pp. 217 and 432, 
1900. 
9 . Alcock, Proc. Roy. Soc., London, vol. 71, p. 275, 1903. 
10. A. F. Cameron and T. I. Brownlee, Quart. Journ. Physiol., vol. 7, 
p. 115; vol. 8, p. 341; voL 9, p. 259. 
11. J. Schmulewitsch, Journ. Anat, vol. 3, p. 218, 1^. 
12. S, J. Holmes, Biology of the Frog, p. 56-58, 1912. 
13. Keith Lucas, Journ. Physiol., vol. 25, p. 448, 1904. 
14. W. M. Bayliss, Principles of General Physiology, pp. 442 and 457, 
1918. 
15. E. J. Marey, Du Mouvement dans les Functions de la Vie, pp. 351- 
358, Paris, 1868. 
16. Carvallo et Weiss, Journ. de Physiol, et de Pathol, gen., vol. 2, pp. 
225-236, 1900. 
Department oe Zoology, 
Iowa State College. 
EXPLANATION OF FIGURES 
Short line between — 7° and — 6 ° is the limlit of the first period, 
20° and 22° is the limit of the second and 42° and 44° is the limit of the 
third period. 
The ordinates represent the height of the tracing of the muscle lever 
in centimeters. The abscissa denote degrees of temperature Centigrade. 
