352 INFLUENCE OF THE CUTANEOUS SECRETIONS 
uninterrupted elimination is a necessary condition for the regular 
continuance of the general functions. Regarded in this point of 
view, the skin may be considered as a dependency of the respira- 
tory apparatus, of which it continues and completes the function, 
by returning incessantly to the atmosphere the combusted products, 
which are water and carbonic acid. 
Therefore the skin, properly speaking, is an expiratory apparatus 
which, under ordinary conditions of the organism, exhales in an 
insensible manner products analogous to those expired from the 
pulmonary surface ; with this difference, that the quantity of car- 
bonic acid is very much less considerable in the former than in 
the latter of these exhalations: according to Burdach, the propor- 
tion of carbonic acid as inhaled by the skin being to that expired 
by the lung as 350 : 23450, or as 1 : 67. 
According to Sanctorius, who wrote at the commencement of the 
seventeenth century, up to our time physiologists and chemists 
have been at great pains to make a comparative estimate, by 
weight, of matters thrown off by the general transpiration (cuta- 
neous and pulmonary); and their researches have shewn the 
quantity to be something considerable, since, according to the first 
of these experimenters, at the middle period of life, the transpiration 
of a man amounts to upwards of 5J pounds in twenty-four 
hours* * * § ; and that out of every eight pounds of solid and liquid 
aliment taken in by a man daily, five pass off by transpiration and 
three only by the alvine and urinary excretionst. 
But the cutaneous and pulmonary transpirations do not 
contribute in equal ratio to these enormous expenditures. Ac- 
cording to Burdach, whose report is founded on Seguin’s experi- 
ments, the first will be to the second as 14155 : 32241 ; that is, as 
i : 2-271. 
So that the loss by the pulmonary surface is double what takes 
place through the tegumentary. On the other hand, the experi- 
ments of Treviranus, Spallanzani, and above all those of Milne 
Edwards, made upon small mammifera or on inferior animals, such 
as frogs, toads, salamanders, or fish, have demonstrated the waste 
by general transpiration to be, in twenty-four hours, little less than 
the half of the entire weight of the body§. 
Without being strictly applicable to our domestic animals, on 
which the like experiments have not yet been made, these ex- 
perimental results are, nevertheless, sufficient to convey a notion 
of the powerful action of the cutaneous secretions on the entire mass 
of the organism ; and to forewarn us that there must exist similar 
* Burdach, Traite de Physiologie, vol. vii, p. 354. 
f Richerand and Berand, Nouvcaux Elements de Fhysiologie, v. ii, p. 10*2. 
X Berand, loe. cit. p. 302. 
§ Burdach, loc. cit. p. 357. 
