Discussion 77 



between rate of sweating and the concentration, because it varies 

 enormously. 



Thaysen: Yes, that is very important. Secretory rate must be con- 

 trolled in all work on electrolyte composition of secretions, and compara- 

 tive studies can only be made on the basis of standard rates. This is of 

 course equally important whether one states the result in absolute con- 

 centrations of sodium and potassium or as the Na/K ratio. When the 

 developing organism is under study, secretory rate must be expressed per 

 unit weight of gland or some other parameter allowing for the influence 

 of growth. I believe that negligence of these important factors is the 

 main reason why the literature on variations with sex and age in the 

 secretion of electrolytes is, largely speaking, inconclusive and frequently 

 mutually conflicting. 



With respect to Dr. Karvonen's remark I should like to add this com- 

 ment. I take it that the sweat tests have been done in the usual way, i.e. 

 with collection of sweat from a smaller or larger area of the skin, not 

 from individual glands, and that the difference between the men and 

 women is stated on the basis of comparable sweating rates per unit area 

 of the skin. It does tell us, then, that there is a difference between sweat- 

 ing of men and women, but it does not tell us anything about the reason 

 for the difference. As is well known, the number of functioning sweat 

 glands per unit area of the skin varies between individuals, between the 

 sexes and with age, as well as between different skin regions in the same 

 person. Comparable rates per unit area of the skin are therefore not 

 necessarily the same as comparable rates per gland. Physiologically it is 

 of course the rate per gland that matters and not the rate per unit skin 

 area. Let us take it that women have half the number of glands per 

 unit skin area that men have. Since the rate per unit skin area was 

 comparable, the mean flow per gland in the women would then be twice 

 that in the men. A higher sodium concentration in the swxat of the 

 women might therefore merely be due to the fact that secretory rate per 

 gland was larger. Let us take it that the men and women had an equal 

 number of glands per unit skin area. In that case the difference between 

 the sexes could not be due to a difference in the rate per gland, but 

 might well be due to hormonal or other factors. What I mean is that in 

 comparative work it is a prerequisite to determine not only secretory 

 rate, but also the number of functioning glands, if you want to make 

 deductions from your findings. A method for determination of the 

 number of functioning glands within the area of sweat collection has 

 been published by Dole and Thaysen (1953. J. exp. Med.. 98, 129). 



