414 PEACTICAL PHYSIOLOGY 



Sweating in Man. The palm of the well-washed hand is pressed 

 on to paper sensitised with silver nitrate. Spots of silver chloride, 

 formed at the mouths of the sweat glands, become visible on the paper. 

 A pad soaked in atropine solution 1 per cent, is fixed with collodion on a 

 small piece of the palm. No sweat spots will be obtained from this 

 piece next day. The local subcutaneous injection of pilocarpine pro- 

 vokes sweating. 



On a warm day one hand is held for 10' in water at 45 C. and the 

 other in water at 20 C. Exercise is then taken. The hand which 

 was in the warm water will not sweat for some time. The terminal 

 sweat apparatus is depressed by either excessive cold or heat. 



Measurement of Cutaneous Excretion (Barratt's Method). A glass 

 plethysmograph provided with entrance and exit tubes and a rubber 

 collar is fitted on to the fore-arm. 



The exit tube is connected with weighed Haldane-Pembrey absorp- 

 tion tubes : (A) Sulphuric acid, (B) soda-lime sulphuric acid. The 

 entrance tube passes through soda-lime bottles and pumice-sulphuric 

 acid. Air is drawn through the apparatus by a filter pump and 

 a meter is interposed. A rate of 1 litre per minute is sufficient. 

 After a half hour the increase of weight in A and in B is determined. 

 The increase in A gives the amount of water and in B the amount of 

 of C0 2 excreted. The excretion of water is diminished by painting tho 

 skin with 20 per cent, carbolic acid and producing dry dermatitis. 



