Return of Function of Sweat Glands After Cutting or Crushing Sympathetic Nerves. ∗

Abstract

Although considerable information is available concerning the regeneration of somatic nerves and the return of functions controlled by them, little is known concerning the regeneration of peripheral autonomic nerves. 1 The galvanic skin reflex and measurements of changes in cutaneous resistance and temperature when used as indices give information on whether regeneration is taking place but these methods do not give information quantitatively, on the extent of the return of peripheral autonomic activity which has taken place. 2

In the present experiments measurements of the rate of sweating in the pads of the paws of cats have been made before and after the sympathetic nerves to them have been cut, to provide such data. The method is that of Neumann, Cohn and Burch, 3 adapted to the needs of these experiments. The hind paw is enclosed in an air-tight chamber through which is passed a continuous stream of dry oxygen. The dry gas takes up water lost by the paw and carries it into a tared metal coil immersed in a freezing mixture of alcohol and solid CO₂. The water suspended in the gas is deposited in the coil. After a suitable collection period (15 minutes) a new coil is substituted so that the collection of the water is continuous. The water-laden coil is dried and weighed. The difference in the weights before and after removal of water represents the water output for the period of collection. The method is accurate to 3%.

The water output from the pads of the normal right and left hind paws (area of paw approximately 30 sq cm, area of pad approximately 6 sq cm) was measured in 25 animals. When animals are at rest and the body temperature is normal (37 to 38.5° C) the water output reaches a basal level of 7 to 10 mg/15 min. This amount represents water lost by evaporation in the absence of active sweating from the pad.