The Influence of Extraneous Factors 57 



1938); sulphonamides provide a similar example (Farrell, Lyman 

 and Youmans, 1938; Kuehnau, 1939; Hug, 1940). 



Marked spermicidal power is characteristic of a great many sur- 

 face-active agents, quinones and heavy metal compounds. A tech- 

 nique for assessing the spermicidal activity of pure substances has 

 been developed by Baker (1931, 1932, 1935) whose so-called 'killing 

 concentration' is the lowest one capable of killing all spermatozoa 

 suspended in a buffered glucose-saline solution (Baker's solution) 

 within half an hour, at body temperature, under standard conditions 

 in vitro. Of the many substances examined by Baker, the most 

 highly spermicidal was phenylmercuric acetate (killing concentra- 

 tion 0-001%). Various quinones such as toluquinone, butylquinone, 

 methoxyquinone, parabenzoquinone, ethylquinone and paraxylo- 

 quinone were also strongly spermicidal. Lower down the scale were 

 mercuric chloride, methoxyhydroquinone, formaldehyde, methyl- 

 hydroquinone, saponin, and hexylresorcinol. A critical account of 

 the existing methods for testing the efficiency of spermicidal com- 

 pounds is given by Millman (1952), Davidson (1953) and Gamble 

 (1953). 



As to the mode of action of surface-active agents, such as e.g. 

 cetyltrimethylammonium bromide, cetyldimethylbenzylammonium 

 chloride, /7-tri/5opropy Iphenoxypolyethoxyethanol, dodecyl sulphate, 

 various condensation products of long-chain fatty alcohols with 

 ethylene oxide, and the numerous other ionic and non-ionic deter- 

 gents, there is some evidence to show that these substances act 

 directly on the constituents of the so-called lipid capsule, i.e. the 

 lipid-containing outer layer which protects the surface of the sperma- 

 tozoon. The mechanism of the spermicidal activity of detergents on 

 the sperm may be likened to the haemolytic action of surface-active 

 compounds on the erythrocytes, or the bactericidal effects of these 

 substances on various microorganisms. The changes brought about 

 by detergents manifest themselves in a loss of motility and fructo lytic 

 power, and in a grossly altered permeability of the sperm cells as 

 indicated by the leakage of cytochrome c. In contrast to intact 

 spermatozoa, the respiration of sperm cells treated with suitable 

 concentrations of detergents is markedly increased by succinate 

 (Koefoed-Johnsen and Mann, 1954). 



As to the action of some at any rate, of the many other 



