xiv The Biochemistry of Semen 



on the blood supply. Nature has endowed the spermatozoa with the 

 means of very efficient utilization of extraneous sources of energy, 

 such as are accessible to the sperm cells either in their natural 

 environment, the seminal plasma, or in the artificial storage media. 



As will be evident from what follows later, the present century 

 has witnessed much that is new in the field of semen biochemistry. 

 By and large, however, the situation is not very different from what 

 it was two centuries ago, when Charles Bonnet addressed the follow- 

 ing remarks about spermatozoa to Spallanzani: 



'They are, of all animalculi of liquids, those which have most 

 excited my curiosity: the element in which they live, the place of 

 their abode, their figure, motion, their secret properties; all, in a 

 word, should interest us in so singular a kind of minute animated 

 beings. How are they found there, how are they propagated, how 

 are they developed, how are they fed, and what is their motion? 

 What becomes of them when the liquid they inhabit is reabsorbed 

 by the vessels and returned to the blood? Why do they appear only 

 at the age of puberty; where did they exist before this period? Do 

 they serve no purpose but to people the fluid where they are so 

 largely scattered? How far are we from being able to answer any of 

 these questions! And how probable it is, that future age will be as 

 ignorant of the whole, as our own!' 



