524 OF SECRETION AND EXCRETION. 



red, not with the lowest, but with moderate amounts of moisture in the air. 

 The minimum amount of perspiration always occurred on rising in the morn- 

 ing, being then 25 per cent, below the average. The maximum amount was 

 eliminated at noon, when it rose to 52 above the minimum. Food invari- 

 ably increased the cutaneous transpiration, coffee and tea having a particu- 

 larly powerful influence. The increase occurred soonest after breakfast, but 

 Avas greatest and most permanent after dinner. Moderate muscular or mental 

 exertion slightly increased the amount of perspiration, but fatigue and ex- 

 haustion produced a considerable decrease. Violent muscular effort raised 

 it to 77 per cent, above the mean; severe intellectual labor, 42 per cent. 

 During sweating, the rise was equal to 116 per cent, over the mean, but after 

 sweating it fell even to 26 per cent, below the mean. The amount of insen- 

 sible perspiration varies greatly with the conditions of the atmosphere, and 

 of the body itself, in respect to exposure, food, exercise, and activity of other 

 secretions ; and these variations, as we shall hereafter see ( 424), have a most 

 important share in the regulation of the temperature of the body. Accord- 

 ing to Garrod, 1 sweating begins when standing at rest at about 86 Fahr. 

 Exact observations on this point, however, in which not merely the temper- 

 ature, but the hygrometric state of the air should be precisely determined, 

 are much wanting; the best hitherto recorded being those made by Dr. 

 Southwood Smith, 2 at the Phoenix Gas Works, in which the former element 

 only was carefully noted. These observations were made upon eight of the 

 workmen employed in "drawing" and "charging" the retorts, and in mak- 

 ing up the fires, during which they are exposed to intense heat ; the men were 

 accurately weighed in their clothes, immediately before they began, and 

 after they had finished their work ; and in the interval between the first and 

 second weighings, they were not allowed to partake of any solid or liquid 

 ingesta, nor to part with urine or fseces. 



Experiment I. Nov. 18th, 1836. Day bright and clear. Temperature of 

 the air in which the men worked, 60 Fahr. Barometer 29.25 in. to 29.4 

 in. Duration of labor, 45 minutes. Average loss of weight, 3 Ibs. 6 oz. ; 

 maximum, 4 Ibs. 3 oz. ; minimum, 2 Ibs. 8 oz. 



Experiment II. Nov. 25th, 1836. Day foggy, with scarcely any wind. 

 Temperature of the air 39 Fahr. Barometer 29.8. Duration of labor, 75 

 minutes. Average loss of weight, 2 Ibs. 2 oz. ; maximum, 2 Ibs. 15 oz. ; mini- 

 mum, 14 oz. 



Experiment III. June 3d, 1837. Day exceedingly bright and clear, with 

 little wind. Temperature of the air, 60. Duration of labor, 60 minutes. 

 Average loss of weight, 2 Ibs. 8 oz. ; maximum 3 Ibs. ; mimimum, 2 Ibs. 



Experiment IV. On the same day, two other men worked in an unusually 

 hot place for 70 minutes; the loss of weight of one of these was 4 Ibs. 14 oz.; 

 and of the other 5 Ibs. 2 oz. 



Although the individuals subjected to those experiments were not in all 

 instances the same, yet there was enough of identity among them to admit 

 of the certain inference, that the amount of fluid lost must be influenced by 

 the state of the individual system, as well as by that of the surrounding 

 medium. Thus in the second experiment, Michael Griffiths lost 2 Ibs. 6 oz., 

 and Charles Cahell 2 Ibs. 15 oz. ; whilst in the third, Michael Griffiths lost 

 3 Ibs., and Charles Cahell only 2 Ibs. It is probable that the amount of 

 liquid ingested not long previously, might have a considerable influence on 

 the quantity lost by transpiration under such circumstances. The most 

 recent investigator into the conditions affecting the evaporation of fluid 



1 Journ. of Annt. and Phys., vol. vi, 1872, p. 130. 



2 Philosophy of Health, vol. ii, pp. 391-396. 



