MACDONNELL on animal dextrine. 
r 
539 
In the following pages it is not intended to advance any theoretic 
views as to its function or ultimate destination in the animal eco¬ 
nomy, hut simply to bring before the reader a resume of what is 
known as to its physiological properties and relations. 
The Amyloid substance of Bernard, or of the first species, is a 
ternary compound, isomeric with dried grape sugar. It is a neutral, 
whitish, inodorous, insipid matter, soluble in water, insoluble in 
alcohol and strong acetic acid. Its solution in water is milky and 
opalescent. 
In the presence of saliva and other animal ferments, it is con¬ 
verted into sugar, which ferments on the addition of yeast, and 
reduces the cupro-potassic solution; iodine in contact with it pro¬ 
duces a peculiar brown colour, more or less intense, disappearing on 
the application of heat, and reappearing when the solution cools 
below 80°; like vegetable dextrine it causes the plain of polarization 
to deviate to the right. 
In order to determine its presence in any tissue perhaps the 
readiest method is to use the microscope. By adding some acidu¬ 
lated tincture of iodine the characteristic brown colour is at once 
produced. This may be dispelled by gently heating the slide, and 
returns when it has cooled. Many of the tissues, however, in 
which it exists, contain it so abundantly that it can be obtained even 
from small portions in sufficient quantity for chemical examination. 
It may be obtained, according to circumstances, by any of the 
following processes :—1st. Alcoholic process. Cut the organ or tissue 
(say the liver of a recently killed rabbit, lately fed on carrots and 
in full digestion) into thin slices and throw them into rather more 
than their own bulk of boiling distilled water, boil for a few minutes, 
then bruise the whole to pulp in a mortar; boil once more for a few 
minutes, throw the whole in a filter, and allow the milky solution, 
which passes through, to fall into four or five times its volume of 
alcohol. The amyloid substance falls as an abundant, white, flaky 
precipitate; any albuminoid matters present are of course precipi¬ 
tated along with it, and must be got rid of by washing the precipitate 
with a strong solution of caustic potash. 
This process is best adapted for tissues in which albuminoid matter 
is not abundant, as the liver, and if instead of using alcohol, methy¬ 
lated spirit be substituted, the amyloid substance may be got in a 
state of tolerable purity at a moderate cost, and at least sufficiently 
pure for many experimental purposes. In this way also the amount 
existing in any liver may be very accurately determined, even without 
the use of the solution of caustic potash, as the quantity of gelatine 
extracted from the liver by so short a time of boiling is very small 
indeed, and does not interfere with general results. 
2nd. Acetic acid process. The organ, or tissue, to be examined is 
boiled is a small quantity of distilled water ; the whole is then bruised 
in a mortar with animal charcoal thrown in a filter, and the droppings 
allowed to fall into glacial acetic acid. The amyloid substance falls 
