THE FUNCTION OF THE CONTRACTILE VACUOLE IN 



PARAMECIUM CAUDATUM; WITH SPECIAL 



REFERENCE TO THE EXCRETION OF 



NITROGENOUS COMPOUNDS. 1 



J. H. WEATHERBV, 

 ZOOLOGICAL LABORATORY OF THE JOHNS HOPKINS UNIVERSITY. 



INTRODUCTION. 



Ehrenberg (1838) was probably the first to consider the 

 function of the contractile vacuole. He asserted that it is a 

 spermatic gland; but no evidence has been found in support of 

 this view. 



Lieberkiihn (1836), Claparede (1834), Lachmann (i856),Siebold 

 and Stannius (1854), and Pritchard (1861) held that it is a 

 rudimentary heart, which, by its pulsations, produces the circu- 

 lation of a body-fluid throughout the organism. The demon- 

 stration by Jennings (1904) that the vacuole communicates 

 directly with the exterior and discharges its contents into the 

 surrounding medium definitely eliminates such an explanation. 



Haeckel (see Kent, 1880, p. 69), Maupas (1863), Biitschli 

 (1887-89), Ehrmann (1894), and others contend that it is a 

 respiratory organelle, or a mechanism for the removal of some 

 of the end products of oxidation; but insufficient evidence has 

 been found to warrant the acceptance of this view. 



Stein and Schmidt (see Kent, 1880, p. 69), Griffiths (1888), 

 Calkins (1909), Khainsky (1910), Woodruff (1911), Minchin 

 (1912), Howland (1924), Nowikoff (1908), Shumway (1917), 

 Riddle and Torrey (1923), Flather (1919), and Marshall (1921) 

 believed the vacuole to be an excretory organelle. This view 



1 This paper is a portion of an essay submitted to the Board of University 

 Studies of the Johns Hopkins University in partial fulfillment of the requirements 

 for the degree of Master of Arts. The writer wishes to acknowledge his indebted- 

 ness to Professor S. O. Mast, who suggested the problem, and under whose personal 

 supervision the work was done; and to Professor E. K. Marshall of the Department 

 of Physiology of the Johns Hopkins Medical School who offered many helpful 

 suggestions in connection with the literature on the enzyme, urease, and the 

 xanthydrol test for urea. 



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