SPERM MOVEMENT PROBLEMS AND OBSERVATIONS 19 



He will, of course, say that the presence of the stationary metal strip 

 will increase the amount of energy needed to keep the oscillating 

 strip going; but unless the strips are ridiculously far apart, that is 

 all he will say. If asked whether he has any other helpful observa- 

 tions, he may mention that there is no reason why a system of oscil- 

 lating strips should get into phase and that there is no reason why 

 such a system should get i)ito a condition of minimum energy ex- 

 penditure. 



It is for these reasons that estimates of sperm energy expenditure 

 and attempts to correlate them with chemical events, such as the 

 breakdown and resynthesis of ATP in the sperm tail, are at present 

 of little value, though, as mentioned before, it is difficult to resist 

 doing the sums. One thing is fairly certain: under anaerobic condi- 

 tions, there is not much energy to spare. If oxidative phosphoryla- 

 tion is allowed to occur, there is plenty of energy, unless one arti- 

 ficially increases the density of the suspension and, therefore, the 

 viscosity of the system, or the viscosity of the suspending medium. 



ATP, ETC. 



It has been known for a little under twenty years that ATP is in- 

 volved in sperm motility, but measurements of ATP have so far been 

 confined to just ejaculated spermatozoa, very tired spermatozoa, or 

 motionless ones. I thought it might be of interest to see how the ATP, 

 adenosine diphosphate (ADP), and adenosine monophosphate (AMP) 

 content of bull spermatozoa varied under anaerobic conditions and, 

 at the same time, to measure their activity by the impedance change 

 frequency method (Rothschild, 1948) and heat production (Roths- 

 child, 1960). Neither of these methods actually measures activity but 

 some property associated with activity. When doing these experi- 

 ments, I was, therefore, once again reminded of the importance of 

 developing an objective way of measuring sperm activity at physio- 

 logical densities, something which, so far, has defeated us, unless 

 the Rikmenspoel (1957) method meets the situation, which is doubt- 

 ful because it involves a rather severe dilution of the semen. Al- 

 though it is true that when bull spermatozoa have stopped swimming 

 their ATP content is reduced, no detailed information about bull 

 sperm nucleotide metabolism has, so far, been published. In experi- 

 ments I am doing in collaboration with Dr. A. A. Newton, with 



