April 12, 1873.] 
. THE PHARMACEUTICAL JOURNAL AND TRANSACTIONS. 
807 
passes by conduction along the wire to the glass, through 
which it spreads from the centre outwards. You see a 
beautiful black cross inclosing four luminous quadrants 
growing up and becoming gradually black by comparison 
upon the screen. And, as in the case of pressure, we pro¬ 
duced colours, so here also, by the proper application of heat, 
gorgeous chromatic effects may be produced. And they 
may be rendered permanent by first heating the glass 
sufficiently, and then cooling it, so that the chilled mass 
shall remain in a state of strain and pressure. Two or 
three examples will illustrate this point. The colours, you 
observe, are quite as rich as those obtained in the case of 
crystals. 
(To be continued.) 
THE USE OF GELATIN IN NUTRITION.* 
BY CARL VOIT. 
The author begins this paper by a discussion of the 
experiments made by previous observers on the use of 
gelatin as food. He considers that those of Edwards and 
Balzac and of Magendie were vitiated by the fact that 
they allowed the animals on which they experimented to 
eat their food instead of administering it to them by force. 
Disgust at the gelatin prevented the dogs from eating it, 
and they preferred to die of hunger. Yoit, however, has 
noticed some dogs do the same with raw meat, and others 
with bread. His own experiments were made by feeding 
dogs on gelatin and flesh, or gelatin alone, on gelatin 
and fat, on flesh and fat, or flesh, gelatin and fat, and 
observing how much flesh underwent transformation in 
the organism as indicated by the nitrogen excreted, and 
how much was lost or gained by the body. The results 
showed that gelatin always saves albumin, and does so to 
a much greater extent than fat or carbohydrates. In a 
large dog 168 pai'ts of dry gelatin supplied 84 of dry flesh 
or albumin. An increase in the quantity of gelatin in the 
food was followed by a greater saving of albumin ; but the 
saving cannot be carried beyond a certain limit, for even 
when the greatest possible quantity of gelatin is adminis¬ 
tered and much fat in addition, some albumin from the 
body or the food still undergoes decomposition. The 
saving effect of gelatin is greater when fat is given along 
with it. No permanent deposition of gelatin in the 
organism takes place ; but the whole of it undergoes 
rapid decomposition. The nitrogen of all the gelatin 
given could be found in the urine and faeces within twenty- 
four hours, and only in one large dog were there indications 
that a small portion of the gelatin remained after this 
time, but was decomposed on the following day. This is 
possibly connected with the simultaneous administration 
of much fat, which may perhaps hinder the rapid decom¬ 
position of large quantities of gelatin. It cannot be that 
gelatin spares albumin by supplying the waste of gelati- 
genous tissues instead of letting this be done by albumin, 
because we must then assume that the gelatin is not 
completely decomposed ; and if this be the case, the 
amount of nitrogen excreted would show that there is no 
saving of albumin, and no advantage would be gained. 
Gelatigenous tissues cannot be formed from gelatin, but, 
as their development shows, only from albuminous bodies. 
The author then gives a full account of his opinions re¬ 
garding albumin in the organism. When a dog is allowed 
to fast for several days, the amount of albumin daily 
destroyed in the body will be e.g., 0’8 per cent, of that 
contained in it. When well fed with albumin, the same 
dog will daily decompose 9 per cent, of albumin. This 
clearly shows that the relations of the albumin in the 
body to decomposing agencies are very different. Voit 
therefore divides it into (1) circulating albumin, or albumin 
in the circulating plasma or lymph ; (2) organ-albumin. 
* Zeitschrift fur Biologie, viii. 297—388, and from the 
Journal of the Chemical Society. 
The first sort undergoes rapid decomposition. It might 
have been called plasma-albumin, but the name of cir¬ 
culating albumin was chosen in order to indicate that it 
is during circulation through the tissues that this albumin 
comes under the conditions of decomposition. The albumin 
of blood-plasma is plasma-albumin ; but only a small part 
of it is decomposed, because the greater part of it is in a 
state of firmer combination as organ-albumin of the blood. 
Organ-albumin is not decomposed as such, for it is not 
subjected to the conditions of decomposition until it has 
undergone conversion into circulating albumin. When the 
equilibrium between the organ-albumin and circulating 
albumin is suddenly disturbed, so that the proportion of 
the former is increased e.g., by venesection, the excess of 
organ-albumin is not retained by the organism, but is con¬ 
verted into circulating albumin and decomposed. The 
author does not agree with Fick in his supposition that it 
is not albumin but peptones that are rapidly decomposed 
in the organism. Eick compares the rapid decomposition 
in the body which occurs after albuminous food has been 
taken to the blaze which occurs when a rapidly combus¬ 
tible body like gunpowder (to which he compares peptones) 
is mixed with a slowly combustible one like charcoal 
(which would represent albumin). Yoit would rather 
compare it to a blaze on the addition of fine chips of wood 
to a burning log of the same kind. He considers the 
notion to be an unfortunate one that absorption in the in¬ 
testine takes place by osmosis, and that albuminous bodies 
must, therefore, be converted into peptones before they 
can be absorbed. He is unable to see why it should be 
supposed that albuminous substances cannot pass through 
the intestinal walls when they readily do so through every 
possible membrane and organ. The albumin in the food 
is chiefly decomposed in the plasma current, but part of it 
serves to replace organ-albumin which has been destroyed, 
or as a deposit. According to the doctrine of luxus-con- 
sumption also, a small quantity only of albumin is decom¬ 
posed in the organs, but the replacement of this only is 
necessary, and any additional supply is luxus, and under¬ 
goes combustion in the blood as a surplus. According to 
Voit, very little albumin is decomposed during fasting, 
but every supply of albumin in the food increases the 
stream of plasma to the organs, and so much albumin is 
thereby subjected to the conditions of decomposition. 
The rich supply is not luxury (luxus), but a necessity if 
the body is to retain a definite amount of albumin. 
The simplest explanation of the fact that gelatin, like 
fat and carbo-hydrates, cannot entirely arrest the trans¬ 
formation of albumin in the body is, that it cannot replace 
the decomposed organ-albumin or construct new organs or 
tissues, not even gelatigenous tissues. In this respect it 
behaves exactly like peptones. It lessens the conversion 
of organ-albumin into circulating albumin ; when given 
alone it diminishes the loss of albumin from the organism ; 
and when given along with albumin in food, it lessens the 
proportion of albumin which undergoes decomposition, so 
that a much smaller quantity suffices to supply the needs 
of the body. 
Gelatin differs from other nutriments inasmuch as it 
cannot replace any of them; fat and carbohydrates can 
completely prevent the loss of fat from the body, and each 
inorganic constituent the loss of a similar one, but gelatin 
does not totally prevent the loss of albumin, but only of a 
part of it. Gelatin does not lessen the loss of fat from 
the body to the same extent as carbohydrates, the amount 
of carbonic acid excreted remaining nearly the same. 
When gelatin is given along with meat, it not only 
lessens the consumption of albumin, but also diminishes 
that of fat, though only to a small extent; it does not 
economise fat by taking up the oxygen which would other¬ 
wise oxidize it, since 200 parts of gelatin do not economise 
74 parts of fat which on this supposition it ought to do, 
since these proportions of gelatin and fat require the same 
amount of oxygen for their complete oxidation. 
Voit criticizes Liebig’s division of food into plastic and 
respiratory, which he considers to be quite erroneous. 
