Discussion 75 



theoretical interest that this is a disease which manifests itself primarily 

 in the lungs and pancreas with gross pathology, and yet has this very 

 subtle physiological pathology in the sweat glands. Have you done any- 

 thing with that type of patient? 



Thaysen: Yes, but I never did much with them. We did find a very 

 high sodium concentration in their sweat. 



Wallace : A high sodium concentration in sweat is found in nephrosis, 

 and Dr. Warming-Larsen of Copenhagen has studied this problem. The 

 nephrotic child gaining oedema has a high sodium concentration in the 

 sweat yet a very small sweat volume ; but overnight, as he diureses, he 

 puts out an increased volume of sweat yet at the same time the sweat 

 sodium concentration falls. The net amount of sodium lost from the 

 sweating skin is the same whether he is oedematous or not. I would like 

 to know about the relation of ADH to sweat volume ; does ADH control 

 the sweat glands as well as the kidney? 



Thaysen: That is interesting. Off-hand one would have guessed that 

 the sodium concentration of the sweat would have been low during 

 the phase of oedema formation and high when the patient started to 

 diurese. That would agree with what we know about the action of aldo- 

 sterone on the glands and with the results of sweat and saliva analyses 

 in other oedamatous states. Since the quantity of sodium excreted per 

 unit area of the skin per unit time remained constant, whereas the volume 

 of sweat increased when the child diuresed, an ADH effect might be a 

 possibility worth considering. However, as far as I am aware, it has been 

 shown that ADH has no effect on the volume of sweat produced ( Ama- 

 truda, T. T., Jr., and Welt, L. G. (1953). J. appl. Physiol, 5, 759; Pearcy 

 et al. (1956). J. appl. Physiol, 8, 621). 



Adolph : Can somebody clarify the reports that tears are very hyper- 

 tonic when they are formed? 



Davson : I did some analyses a long time ago, and we discovered that 

 the chloride concentration was equal to that of the blood. It is a very 

 difficult problem obtaining tears, because you have got to make the 

 person cry very hard to get enough to do an analysis. 



Thaysen: In 1889 Massart {Arch. Biol, Paris, 9, 537) applied sodium 

 chloride solutions of varying concentration to the conjunctival sac of a 

 few test subjects. He never analysed the tear fluid, but from the reac- 

 tions of the test subjects to the different solutions he concluded that a 

 1-3 per cent solution of sodium chloride was isotonic with the tears. 

 According to Krogh and co-workers (1945. Acta physiol scand., 10, 88) 

 this experiment forms the only basis for the rather widespread statement 

 in physiological and pharmacological textbooks that tears are hypertonic 

 as compared to the plasma. In 1945 Krogh measured the osmotic pres- 

 sure of tears and found them to be isotonic. The finding w as confirmed 

 by Giardini and Roberts in 1950 {Brit. J. Ophthal, 34, 737). 



Black: If you inject ^^K intravenously and then collect serial samples 

 of saliva you find that the specific activity of potassium in the saliva is 

 several times that of the specific activity of the potassium in plasma at 

 the same time. This behaviour is analogous to that in urine and suggests 

 to us that the potassium in saliva is, like that in urine, secreted by cells. 



