180 THE PHYSIOLOGY OF REPRODUCTION 



Ballowitz expresses the opinion that the circles described 

 by insects' sperms are -simply the modified spirals made by the 

 free-swimming cells. BuUer thinks that this view, which pro- 

 vides a purely mechanical explanation, is also probably correct 

 for the spermatozoa of Echinoderms. 



Since counter-clockwise rotation upon surfaces has been 

 observed in the spermatozoa of two groups as widely separate 

 as the Insecta and the Echinodermata, it would seem probable, 

 as BuUer remarks, that it will be found to occur in other animals. 



The spermatozoa of Mammals, in traversing the female 

 passages after copulation, make their way upward towards the 

 ovaries in opposition to downward currents set up by the ciha 

 of the hning epitheha. Kraft ^ has shown that when rabbits' 

 spermatozoa, in a state of feeble motion, are placed upon the 

 inner waU of the oviduct, their movements become more 

 vigorous and they swim against the current which the ciha pro- 

 duce. Roth ^ also has succeeded in experimentally illustrating 

 the same fact. 



It is commonly stated that in Man the passage of the sperma- 

 tozoa from the vagina inwards is assisted by a contraction of 

 the muscular wall of the uterus, which compresses the cavity of 

 that organ into which the sperms are drawn when relaxation 

 takes place. ^ The contraction of the uterus is said to be a 

 reflex action resulting from copulation. It has also been sug- 

 gested that, during copulation, a mucous plug which is ordinarily 

 contained in the cervix may be temporarily and partially ex- 

 pelled into the vagina and afterwards withdrawn with the 

 spermatozoa adhering to it.* 



So also Heape ^ has shown that in the rabbit the passage of 

 the spermatozoa into the uterus is probably assisted by a sucking 



' Kraft, " Zur Physiologie des Flimmerepithels bei Wirbelthieren," 

 Pfiuger's Arehiv, vol. xlvii., 1890. 



' Roth, " Ueber das Verhalten beweglicher Mikroorganismeu in stromender 

 Flussigkeit," Deutsche med. Wochenschrift, vol. xix., 1893. Verworn [loo. cit.) 

 describes this property of spermatozoa under the name of rheotaxis, which, 

 he says, is a special kind of barotaxis. See also Adolphi, " Die Spermatozoen 

 der Saugethiere schwimmen gegen den Strom," Anat. Am., vol. xxvi., 1905. 



' See Beck, " How Do the Spermatozoa enter the Uterus ? " Amer. Jour, of 

 Obstet., vol. viii., 1875. 



* See Williams, Obstetrics, New York, 1904. 



' Heape, " The Artificial Insemination of Mares," Veterinaricm, 1898. 



