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CARNEGIE INSTITUTION OF WASHINGTON. 



tract at different times. Also, it was suggested that these secretions 

 may act in a different degree upon the male-forming and upon the 

 female-forming sperm. The female-forming sperm with its larger 

 amount of functional chromatin offers more opportunity to produce 

 physiological incompatibilities and therefore to be eliminated than the 

 smaller male-forming sperm. 



It has long been known that the hyperacidity of the vaginal se- 

 cretions is a powerful factor in producing sterility. Evidence also ex- 

 ists that before pregnancy the os of the uterus is so small that there is 

 little, if any, opportunity for the slightly alkaline secretions of the 

 uterus to mingle with and neutralize the acid vaginal secretions. After 

 the first birth the os is often enlarged or torn and more chance for ad- 

 mixture of the secretions exists. Since acidity is known to be harmful 

 to sperm, and since the selective and eliminating power of the 

 vaginal secretions might, by alterations of its acidity, be changed, it 

 seemed of interest to determine what was the behavior of sperm in 

 various concentrations of acid. For this purpose glacial acetic acid 

 was chosen. The work was planned and carried out by Dr. Little with 

 the assistance of Miss Marion Gibbons. 



The results are tabulated below. Control drops were used on the 

 same microscope slides with the treated drops. Each test was 

 repeated three times. The sperm was kept in warm Ringer's solu- 

 tion. The different reactions of the various sperms are striking. 



Table 7. — Reactions of spermatozoa of vai'ious maynmals to acid solutions. 



Since the mouse and rat sperm-cells are easily distinguishable in 

 size, a mixture of the two was made and treated with solutions of 

 acetic acid as follows: 



