Methods employing various types of capsules for the measurement of sweat volume and for the collection of sample sweat were studied; the filter paper method was found to be the most reliable and easiest to use among the methods examined. Using the filter paper method, sweat volume as well as sweat chloride content from a small skin area were measured during the sweating response to a high environment temperature. The following results obtained:
(1) Individually reproducible response patterns were observed both for sweat volume and sweat chloride content, suggesting a classification of the patterns into four types. Type I: Large sweat volume with high chloride content. Type II: Large sweat volume with low chloride content. Type III: Small sweat volume with high chloride content. Type IV: Small sweat volume with low chloride content.
(2) Determinations on various parts of body revealed that regional variations exist in sweat chloride content. In general, sweat chloride content declines according to the following order: head and neck, middle line on the chest, pectoral region on the chest, forearm (flexor and extensor side) and back of hand; this sequence is the same for most subjects.
(3) Year around experiments have demonstrated clear seasonal fluctuations in sweat chloride content. In all 12 subjects (5 males, 3 females and 4 children), sweat chloride was much higher in winter than in summer. It generally began to rise in early September, (in some subjects during end August) toward high winter levels, and fell toward low summer levels from May on. Sweat chloride content were much higher in all adult males, especially in the winter, than in females and children. This resulted in wider seasonal fluctuations in sweat chloride in men than in women and children.
(4) These seasonal fluctuations in sweat chloride content were observed to follow the same pattern in the various regions of the body.
(5) The parallel relation between sweat rate and sweat chloride content was exhibited less markedly in subjects who secrete sweat of dilute concentration, and vice versa. This relationship could also be applied to seasonal changes in sweat chloride excretion.
(6) It was demonstrated that the sweat chloride level is correlated negatively to the degree of vascular responsiveness as measured by a vascular reaction test to cold.
The findings obtained are thought to support strongly the idea that the chloride excretion in sweat is controlled mainly by the systemic effect of climatic conditions through its influence upon salt reabsorption activity of the gland. It was also suggested that the ability of sweat glands to excrete chloride may be closely related to the other thermoregulatory functions.