ORGANIC 
This is evaporated to dryness in a water-bath. 
It is carefully weighed and the total solid con- 
tents determined; the loss indicates volatile 
matters consisting almost entirely of water. 
The residue is carefully incinerated with the 
usual precautions until all traces of carbon 
are removed: on weighing again we obtain 
the fixed saline constituents. 
By this means we have determined 
Water and volatile matters. 
Organic matters and ammoniacal salts. 
Fixed saline matters. 
The quantity of each organic substance has 
now to be estimated. We have at present no 
absolutely exact method of determining all the 
ingredients from one portion only of a fluid ; 
the following offers the nearest approximation. 
a. Fibrin separates by spontaneous coagula- 
tion; it is washed and determined in the manner 
to be described hereafter. 
__ 6. If casein and albumen be both present, a 
given portion of the clear liquid is acidulated 
with a few drops of acetic acid, and evaporated 
_ to dryness in vacuo over sulphuric acid. The 
_ residue is digested with successive portions of 
_ water at 120°, as long as any thing. dissolves ; 
_ this residue is then dried upon a water-bath, 
| pulverised, and treated with ether, by which 
_ all fatty matters are removed; casein alone 
remains behind. It is completely dried, weigh- 
_ ed, incinerated, and the ashes deducted. This 
method of separating the casein is imperfect, as 
_ a portion of this substance generally redissolves 
_ on the addition of water. If uric acid be pre- 
sent, it will be found with the casein, which 
_ must be dissolved in solution of potash, diluted, 
filtered, supersaturated with acetic acid, by 
which the azotised matter at first precipitated 
| is redissolved. Uric acid alone remains; it is 
‘A collected on a weighed filter, and the quantity 
| determined. It should always be tested by the 
microscope or by nitric acid. 
_ c. The aqueous solution filtered from the 
‘casein, or the liquid for examination, if this 
principle be absent, is evaporated to dryness 
by a water-bath. If much fat is present, the 
residue is washed with ether to remove the 
‘greater part of the oily matter, then dried tho- 
roughly, and powdered; an operation which, 
“after the preliminary treatment with ether, may 
be effected without much difficulty. The pul- 
verized mass is digested with ether, and the 
ethereal solutions, including that in which the 
casein was digested, are mingled and evapo- 
rated to dryness. Cholesterin, fatty matters, 
lactates, and a trace of urea are obtained; 
by digesting with water the cholesterin and 
fats alone remain and may be collected on a 
filter and weighed. 
_ d, The residue, after digestion with ether, is 
eased with boiling water; the solution thus 
Obtained may contain urea, sugar, sugar of 
milk, extractive and saline matters,—in short, 
every thing except the albumen, which is com- 
pletely dried and then weighed. When no 
jcasein is present, the uric acid, if any, will 
jaccompany the albumen, and may be separated 
from it in the manner directed for its separation 
ANALYSIS. 797 
e. The filtered liquid is evaporated to dry- 
ness and treated with a mixture of one part of 
anhydrous ether with-two of absolute alcohol, 
by which urea, muriate of ammonia, lactates, 
the alcoholic extractive matters so called, and 
a small part of the sugar, are dissolved. The 
remainder of the sugar, sugar of milk, aqueous 
extractive matters, urates, sulphates, chlorides, 
and phosphates remain behind, forming re- 
sidue (1). 
J. The alcoholic solution is evaporated to 
dryness and weighed: the solid matter divided 
into two portions; one is dissolved in water 
acidulated with nitric acid, and treated with. 
nitrate of silver, by which the chlorine is sepa- 
rated as chloride of silver, and hence the mu- 
riate of ammonia is determined ; from the’ other 
portion we determine the quantity of urea by 
oxalic acid with the usual precautions. Having 
thus determined the weight of the muriate of 
ammonia and of the urea, we infer the defici- 
ency to consist of a little sugar, lactates, and 
alcoholic extract. 
g. The residue (1), which contains sugar, su- 
gar of milk, watery extract, and salts, is boiled 
with proof-spirit as long, as any thing is dis- 
solved ; the solution is evaporated to dryness, 
and if grape sugar be present, half, the residue 
must be dissolved in water and fermented with 
yeast to determine the proportion of this sub- 
stance, and its weight is deducted from the 
weight of the residue left on evaporating the 
spirituous solution; the other half residue is 
incinerated, and the quantity of saline matter 
ascertained; by deducting the weight of the 
sugar and salts we then obtain that of the sugar 
of milk, together with the alcoholic extract, 
from which we possess no exact means of se- 
parating it. It, however, very rarely happens 
that in the same fluid we meet with grape 
sugar and sugar of milk ; the absence of sugar 
will obviously much simplify the method of 
proceeding. 
h. The portion undissolved by proof-spirit 
is dried and weighed; it is incinerated and 
again weighed; the difference between. the two 
weighings gives the quantity of watery extract, 
This will be the general plan of operations 
if it be required to determine the quantity of 
each individual ingredient. From the number 
of operations required, and the destructible na- 
ture of the ingredients, the result, as already 
mentioned, is not rigidly accurate. Frequently, 
however, it is merely necessary to ascertain the 
proportion in which one substance only is 
found; the presence or absence of others being 
all that it is desired to know concerning them. 
We proceed now to the special consideration 
of the different animal principles. 
Fibrin.—Although the identity, in chemical 
composition, of fibrin, albumen, and casein has 
lately been strongly insisted on by Liebig and 
his pupils ; yet, as in their physical properties 
at least, and in the offices they perform in the 
body, they differ considerably, it is frequently 
of great importance to determine the relative 
proportion of each in the fluids and secretions. 
These three principles occur both in the coagu- 
