Bauhaus-Universität Weimar

of the same membranes as the duodenum, are prolongations of its 
How far the contractility of the ducts may contribute to the fre¬ 
quently sudden expulsion of the saliva and tears, is a question which 
I mention merely as requiring further investigation. I may, in con¬ 
clusion, remark, that since the contractility of #the ducts of glands is 
proved experimentally, the spasm of these parts, spoken of by 
physicians, ceases to be a mere hypothesis. 
Life is attended with a constant decomposition of organic matter; 
the causes of this we have already investigated- (Prolegomena). 
We have seen that the action of external stimuli is necessary for 
the continued manifestation of life; that their action produces a 
change in the composition of the organic matter of the body; and 
that, while more important organic compounds are generated, the 
useless ingredients of the substances which suffered decomposition 
are excreted. We know, moreover, that even the conversion of the 
new nutriment into blood is necessarily attended with the excretion 
of useless elements. The apparatus by which these effete matters 
are eliminated, not formed, are the skin and kidneys. The nature of 
the excretions, however, is the subject of our present consideration. 
The organic conditions on which secretion and excretion generally 
depend have been treated of in the section on Secretion. 
Relative quantity of the excretions.—Dr. Dalton (Edinh. New 
Philosoph. Journ. 1832, 1833,) has made a number of experi¬ 
ments in his own person, to determine the proportion which exists 
between the quantity of the aliment and that of the excretions in a 
healthy subject. In the first series, instituted in the month of 
March, and continued during fourteen days, 91 ounces, or nearly 
6 pounds, was the mean quantity of solid and fluid aliment taken 
into the system daily. The average amount of urine excreted 
each day was 4S§ ounces, of faeces 5 ounces, making together 53i 
ounces; so that, provided the weight of the body remained the 
same, the amount of matter exhaled daily by the skin and lungs 
must have been 37è ounces. The second series of experiments 
was instituted in summer, in the month of June; the daily amount 
of solid excreta was then less by 4 ounces; while the quantity of 
the urine was greater by 3 ounces, the quantity of matter carried off 
by exhalation was 44§ ounces,—6 ounces more, consequently, than 
in the spring. In autumn half the daily amount of food was got 
rid of by exhalation. Dr. Dalton calculated that the aliment which 
he took in twenty-four hours, contained about 11§ ounces of carbon. 
Now he estimates the proportion of carbon in the urine at H per 
cent.; it would, therefore, in 4Si ounces amount to T% or a- of an


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