The Influence of Extraneous Factors 11 



(Hayashi, 1945, 1946; Chang, 1949) on spermatozoa is also, partly 

 at any rate, due to similar processes. 



The mechanism of inactivation and senescence induced in sea- 

 urchin spermatozoa by prolonged dilution remains obscure but there 

 is no reason to suppose that it differs intrinsically from senescence 

 in mammalian spermatozoa. In the latter, senescence is known to be 

 associated with certain definite chemical and physical changes, such 

 as oxidation of intracellular sulphydryl groups which are essential 

 for normal motiUty, decrease in the content of adenosine triphos- 

 phate, and increased sperm permeability, which leads to the extra- 

 cellular appearance of intracellular sperm-proteins; it is also probable 

 that an early change in senescence causes swelHng or some other 

 degeneration in the lipoprotein-containing 'lipid capsule' which 

 normally surrounds the sperm cell (see p. 126). It is by no means 

 unlikely that some upset in the progress of ionic exchange reactions 

 involving particularly potassium ions, is also linked with senescence. 



The effect of dilution on mammalian spermatozoa is essentially 

 the same as in the sperm of lower animals. Dilution with small 

 volumes of saline solution produces 'activation' or excitation, a 

 phenomenon well known to Koelliker and other investigators of 

 the XlXth century. The extent of this activation depends of course, 

 on concomitant factors such as pH, temperature, oxygen, and the 

 presence of certain substances. For example, to obtain optimal 

 motility and metabolism in diluted bull sperm. Lardy and Phillips 

 (1943^) advise the addition of at least 0'005m potassium and 0-012m 

 magnesium, with simultaneous omission of calcium ions. The need 

 for potassium ions has been re-emphasized by Blackshaw (1953). 

 The inclusion of phosphate, mainly as a buffer, has been advocated 

 repeatedly by several authors, even though in higher concentrations 

 it depresses motility and respiration of bull sperm (Bishop and 

 Salisbury, 1954). Sulphate ions have been recommended by Milo- 

 vanov on the ground that they prevent the swelling of spermatozoa 

 and protect the 'lipid capsule' from the action of sodium chloride. 

 In the writer's laboratory, the following salt solution, similar 

 in composition to the Krebs-Henseleit-Ringer solution, is used 

 routinely as a diluent for ram and bull spermatozoa, 100 ml. 

 0-9% NaCl, 4 ml. 1-15% KCl, 1 ml. 2-11% KH2PO4, 1 ml. 3-82% 

 MgSO.-VHaO, 2 ml. of a 1-3% solution of NaHCOg saturated with 



