INTRODUCTION 



Before I decided to embark upon the business of studying the 

 metabolism of semen, my interest used to centre on very different 

 biochemical problems; earlier on, in the laboratory of J. K. Parnas, 

 I was youthfully grappling with the intricacies of intermediary 

 carbohydrate metabolism in muscle, blood and yeast; later on, at 

 the Molteno Institute, in happy association with D. Keilin, we were 

 investigating the nature and function of metalloprotein enzymes in 

 plant and animal tissues. When confronted with the opportunity of 

 an extensive study of spermatozoa, I did not hesitate to give up my 

 former pursuits in order to devote myself to experiments involving 

 biological material which offers the investigator a chance, almost 

 unique so far as mammalian tissues are concerned, of correlating 

 chemical and metabolic findings with clearly defined and highly 

 specific criteria of physiological activity, such as the motility and 

 fertilizing capacity of the spermatozoa. Among other peculiarities 

 which make semen such a fascinating and attractive object of study 

 is that it represents an animal tissue with but a single type of cells, 

 the spermatozoa, freely suspended in a fluid medium of some com- 

 plexity, the seminal plasma, and not subject to cellular growth, 

 division or multiplication; thus, making it feasible to express all 

 one's metabolic measurements directly in terms of cell numbers, 

 without recourse to cumbersome and often unreliable standards such 

 as dry weight of tissue, nitrogen content, or indeed, any other of the 

 commonly used metabolic indices. From the purely practical point 

 of view, which matters greatly, the ability of spermatozoa to 'survive', 

 i.e. retain their remarkable properties under conditions of long-term 

 storage in vitro, is of great importance. This in turn, gives one a 

 chance of exploring at will and under well-defined conditions in 

 vitro, the intricate chemical mechanism underlying the viability, and 

 ultimately, the senescence, of living animal cells. 



So far as the nutrition of spermatozoa is concerned, semen 

 resembles more a suspension of microorganisms in a nutrient 

 medium, than other animal tissues which rely for their nutrients 



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