174 EDWIN J. COHN. 



the season, 70 F. to 73 F., at which this species spawns in Italy, 

 had lost its fecundatory influence at the end of six hours; but 

 that in the temperature of an ice house, 40 F., it retained its 

 efficacy for 25 hours" (Newport, G., 1853, p. 235). Observa- 

 tions of this kind were repeated by Prevost and Dumas (1824) 

 and Newport (1851 and 1853) who wrote: 'The general con- 

 clusion which seems to be deducible from a comparison of the 

 observations of Spallanzani and of Prevost and Dumas, with those 

 by myself, in regard to the tail-less Amphibia, is, that . . . the 

 vitality of the spermatozoon, and the duration of its fecundatory 

 power, are in a ratio inverse to that of an increase of temperature 

 in the surrounding medium" (Newport, G., 1853, p. 237). 



HYDROGEN ION CONCENTRATION. 



Nor was temperature the only environmental factor that was 

 known to effect the physiological condition of the spermatozoon. 

 In a classic paper, " Physiologische Studien iiber die Samen- 

 fliissigkeit" (Koelliker, A., 1856), Koelliker demonstrated that 

 the effect of substances supposedly "harmful" to the activity 

 of the sperm, disappeared if the solutions were first made isotonic 

 and isohydric with the suspension. He understood that a slightly 

 acid solution might inhibit the activity of the sperm without 

 killing them, and that reactivation followed upon neutralization 

 of the acidity. He observed that if KOH, Na 2 HPO 4 or blood 

 were added to suspensions of paralyzed spermatozoa motility 

 was recovered. 



That the degree of activity is a function of the hydrogen ion 

 concentration of the sperm suspension has been confirmed by 

 subsequent investigations. In 1907 Giinther (Giinther, G., 

 1907) showed that not only could sperm be reactivated by a 

 decrease in the hydrogen ion concentration, but also that they 

 could be inactivated by an increase in the hydrogen ion concen- 

 tration. He noticed that if a weak electric current is passed 

 through a mammalian sperm suspension the sperm congregate 

 at the positive pole and are there inactive. The hydrogen 

 ion concentration is greatest at the positive pole. If the 

 current is reversed sperm that have been inactive at the pos- 

 itive pole recover their activity and accumulate at the other 



