456 



* KNOW^LEDGE ♦ 



[Dec. 5, 1884. 



this and the loss of his own weight gave the amount 

 exhaled from the lungs. 



He thus found that the largest quantity of insensible 

 exhalation from the lungs and skin together amounted to 

 31 ounces per hour, or b\ lb. per day. The smallest 

 quantity was lib. 14 oz., and the mean was 31b. lloz. 

 Three-fourths of this was cutaneous. 



These figures only show the quantity of insensible per- 

 spiration during repo.se. Valentin found that his hourly 

 loss by cutaneous exljalation while sitting amounted to 

 32-8 grammes, or rather less than 1;^ ounce. On 

 taking exercise, with an empty stomach, in the sun, 

 the hourly loss increased to 89 3 grammes, or nearly three 

 times as much. After a meal followed by violent exercise, 

 with the temperature of the air at 72° F., it amounted to 

 132 '7 grammes, or nearly 4i times as much as during 

 repose. A robust man, taking violent exercise in hot 

 weather, may give off as much as 5 lb. in an hour. 



The third excretion from the skin, the epithelial or 

 superficial scales of the epidermis, is small in weight, but 

 it is solid, and of similar composition to gelatine. It should 

 be understood that this increases largely with exercise. 

 The practice of sponging and " rubbing down " of athletes 

 removes the excess ; but I am not aware of any attempt 

 that has been made to determine the quantity thus 

 removed. 



Does the skin excrete nitrogenous matter that may be, like 

 urea, a product of the degradation or destruction of muscular 

 tissue % 



The following passage' from Lehmann's " Physiological 

 Chemistry," Vol. ii., 389, shows that the skin picks up 

 plenty of nitrogen from somewhere : — " It has been shown 

 by the experiments of Milly, Jurine, Ingenhouss, Spallan- 

 zani, Abernethy, Barruel, and CoUard di Martigny, that 

 gases, and especially carbonic acid and nitrogen, are likewise 

 exhaled with the liquid secretion of the sudiparious glands. 

 According to the last-named experimentalist, the ratio 

 between these two gases is very variable ; thus, in the gas 

 developed after vegetable food, there is a preponderance of 

 carbonic acid, and after animal food, there is an excess of 

 nitrogen. Abernethy found that on an average the collec- 

 tive gas contained rather more than two-thirds of carbonic 

 acid and rather less than one-third of nitrogen." But it 

 appears that less gas is exhaled when there is much liquid 

 perspiration. 



Lehmann's summary of the experiments of Abernethy, 

 Brunner, and Valentin (Vol. ii., page 391), gives the 

 amount of hourly exudation, under ordinary circumstances, 

 as 5071 grammes of water, 25 of a gramme of carbon, 

 and 092 of a gramme of nitrogen. This amounts to 

 21| grammes of nitrogen per day in the insensible perspira- 

 tion; three-quarters of an ounce avoirdupois, or as much 

 nitrogen as is contained in 4^oz. of dried muscle, or more 

 than 1 lb. of natural living muscle. 



That the liquid perspiration contains compounds of 

 nitrogen, and just such compounds as would result from 

 the degradation of nitrogenous tissue, is unquestionable. 

 As Lehmann says (Vol. ii., page 389) " the sweat very 

 easily decomposes, and gives rise to the secondary forma- 

 tion of ammonia." Simon and Berzelius found salts of 

 ammonia in the sweat, that the ammonia is combined 

 both with hydrochloric acid and with organic acids ; that 

 it probably exists as carbonate of ammonia in alkaline 

 sweat. 



The existence of urea in sweat appears to be uncertain ; 

 some chemists assert its presence, others deny it. Favre 

 and Schottin, for example, who have both studied the 

 subject very carefully, are at direct variance. I suspect 

 that both are right, as its presence or absence is variable, 



and appears to depend on the condition of the subject of 

 the experiment. 



Favre describes a special nitrogenous acid which he 

 discovered in sweat, and names it hydrotic or sudoric acid. 

 Its composition corresponds, according to his analysis, to 

 the formula CioHsNOis. 



I have summarised these facts, as they show clearly 

 enough that conclusions based on an examination of the 

 quantity of nitrogen excreted by the kidneys alone (and 

 such is the sole basis of the modern theories), are of little 

 or no value in determining whether or not muscular work is 

 accompanied with degradation of muscular tissue. The 

 well-known fact that the total quantity of excretory work 

 done by the skin increases with muscular work, while that 

 from the kidneys rather diminishes, indicates in the plainest 

 possible manner that an examination of the skin secretion 

 should be primary in connection with this question. 



Seeing that this has been entirely neglected, I am justified 

 in expressing, very plainly and positively, my opinion of 

 the worthlessness of all the modern research upon which the 

 alleged refutation of Liebig's theory of the destruction and 

 renewal of living tissue in the performance of vital work is 

 based, and my rejection of the modern alternative hypo- 

 thesis concerning the manner in which food supplies the 

 material demanded for muscular and mental work. 



I may be accused of rashness and presumption in thus 

 standing almost, if not quite, alone in opposition to the 

 overwhelming current of modern scientific progress. Such, 

 however, is not the case. It is modem scientific fashion, 

 rather than scientific progress, that I oppose. We have too 

 much of this millinery spirit in the scientific world just now ; 

 too much eagerness to run after " the last thing out," and 

 assume, with undue readiness, that the " latest researches " 

 are of course, the best — especially where fashionable physi- 

 cians are concerned. 



CHATS ABOUT GEOMETRICAL 



MEASUREMENT. 



By Richard A. Proctoe. 



(Continued from p. 417.) 



A. We come now to the measurement of areas bounded 

 by curves. Does this involve a new application of the 

 principle you have indicated, or are new principles in- 

 volved ? 



J/. No new principles are involved. In all problems of 

 geometrical measurement you have to determine an amount, 

 and you must do it by dividing up the quantity you wish 

 to measure into parts which you can deal with simply and 

 add together conveniently, — 



A. But that sounds like a truism. 



M. It is one. But you spoke too soon. As a matter of 

 fact, you cannot divide curved arcs or areas bounded by 

 such curves, or curved surfaces, or volumes, into such parts, 



that is where the diiEculty comes in. You must adopt 



some device by which though you necessarily leave out 

 portions of the quantity you are dealing with, you may yet 

 be able to show that those portions can be neglected, 

 became they may be made less than any quantity, however 

 small, which can be named. 



A. Give me an example, — something concrete. 



M. An area bounded by a curved line will be just what 

 you want :— Suppose M X, A Y, two lines at right 

 angles to each other ; A P B a curved arc ; B M perp. to 

 OX, and that the area you wish to determine is that 

 enclosed between the straight lines O A, M, MB, and 



