21 



most frequent Avhen the spermatozoon is in contact with a nest of 

 epithelial cells .... 



"The three types of normal motion are not only distinctive but 

 are always consecutive, i. e., the second follows the first after 

 a period which is apparently determined both by initial vitality 

 and by the favorable or unfavorable character of the medium, 

 while the third has been observed to occur only in individuals which 

 have already developed the second. They apparently constitute a 

 normal cycle. 



"This cycle is open to the theoretical explanation that these 

 types of motion are directly- adapted to the function of the sper- 

 matozoon ; thus, the progressive vibratile motion which is char- 

 acteristic of the earliest period of its existence appears especially 

 suitable for its prolonged journey through the cervix and uterus 

 to the fundus and tube. This is supported by the fact that during 

 this motion it always heads directly against any existing current, 

 and that during this stage of its journey it must under natural 

 conditions be continuously exposed to the faint outward ciliary 

 currents of the mucous membrane of these passages. 



"The undulatory tactile motion which succeeds the progressive 

 vibratile would then be well adapted to the later stage in which 

 the spermatozoon has reached the tube, where its success in conju- 

 gation is dependent on its finding the ovum rather than on further 

 progress. 



"The stationary- bunting type of motion is that which would be 

 demanded by the passage of the spermat07X)on through the egg 

 membrane which has been so often observed in the lower animals. 

 This very plausible explanation is, however, necessarily theoretical 

 and must always remain so, as the conditions which surround the 

 specimen on the field of the microscope vary in so many respects 

 from those in which it accomplishes conjugation in the course of 

 nature; but the practical importance of the study of tj^pes of 

 motion is not affected by their explanation." 



The duration of motility is a variable factor, dependent entirely 

 upon the environment in which the spermatozoa are placed. 

 Within the body they usually sur\'ive at least a week. One author 

 describes a case in which he found living sperms in a Avoman who 

 stated that coition had not been experienced for three and one- 

 half weeks. It has been stated with regard to human sperms, that 

 their motion should continue or be cai)able of being re-established 

 for twelve hours. Gary (35) states, "first, that in their proper 

 medium and at the body temperature the viability of the sperm 

 cells may extend over a period of a few days ; second, that their 

 prolonged vitality is probably dependent upon the normal lime 

 salts of the prostatic fluid ; third, that the sustaining power of 

 the seminal fluid is increased by its undon with the normal secre- 

 tion of the female genital tract." After death of the male animal 

 they retain their motilitj' in the genital tract for twenty-four to 

 forty-eight hours. 



