CHAPTER XVI 

 MASS PHYSIOLOGY OF SPERMATOZOA 



The relation between numbers of spermatozoa present and their 

 functional ability and longevity has long attracted attention, and 

 a large literature has been built up about various aspects of the 

 subject. The general facts seem well estabHshed, but there is much 

 discussion concerning causal relations underlying the observed 

 facts. 



Spallanzani in 1785 made quantitative studies of the amount of 

 seminal fluid necessary to fertilize amphibian eggs. He reports that, 

 while the fluid is active in extreme dilutions, the percentage of 

 fertilized eggs diminishes with such dilutions. Spallanzani did not 

 understand the true nature of the spermatozoon, but his observa- 

 tions are essentially correct. Prevost and Dumas in 1824 found 

 evidence that the spermatozoa are the essential elements of the semi- 

 nal fluid and attempted to repeat Spallanzani 's results. While they 

 obtained indications supporting his conclusions as given above, their 

 results were too variable to allow a precise statement of quantitative 

 relations. 



Gemmil (1900), using sea-urchin sperm, found that the length of 

 the functional life of spermatozoa is directly related to the numbers 

 present: the greater the concentration the longer the retention of 

 ability to fertilize eggs. He records that the duration of vitality of 

 sperm of Echinus varies from 3 to 72 hours according to the degree 

 of dilution, those in the more dilute suspensions dying first. The 

 decrease in vitality he thought to be due to exhaustion by increased 

 movement and to the dilution of nutritive strength of spermatic 

 fluid. He found similar relations concerning the spermatozoa of 

 limpets (Gasteropoda) and of nemertine worms, except that the 

 length of vitality varied with different sorts of sperm. As will soon 

 appear, the work of recent investigators indicates that one cause of 

 the lessened longevity in dilute sperm suspensions is to be found in 



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