DE. PAVY ON SUG-AK FOEMATION IN THE LIVEE. 
603 
or yellowish ; but when in the opposite state, it is thin, transparent, and watery. This 
mantle, of good-conditioned mussels, yields a decoction, which is quite milky from the 
amount of amyloid substance that is present. There is no sugar, and scarcely a prone- 
ness in the mantle itself to produce sugar ; but if a ferment, such as a little saliva, be 
added, in a few moments an abundant production of sugar is the result. 
The amyloid substance appears, from a micro-chemical examination of the liver, to be 
located in the hepatic cells. It belongs only to the healthy or physiological state, and 
may therefore be regarded as the result of a specific functional formation. It is most 
prone to descend by a chemical process into sugar ; but an examination of the liver 
after different diets shows that it is produced, certainly in part, during life from sugar 
and its ally, starch. 
In making a quantitative determination of this material in the liver, I have availed 
myself of its properties of resisting the action of a boiling solution of potash, and of 
being precipitated by spirit. The following results were obtained by pounding a piece 
of weighed liver with potash, adding a little water, and boiling some minutes until all 
was completely dissolved. The liquid was then poured into about six times its volume 
of spirit, by w’hich the amyloid substance was thrown down as a white flocculent pre- 
cipitate. The precipitate, after being well washed with spirit, was dried and weighed. 
The size of the liver is to a most striking extent influenced by the nature of the diet ; 
and the alteration that is thus induced is chiefly, if not entirely, due to the amount of 
amyloid substance present. I was first conducted to the discovery of these facts, whilst 
in my early experiments I was seeking to determine if the quantity of sugar found in 
the liver and blood of the dog after death was altered from its ordinary amount by the 
previous administration of a strictly vegetable diet. The process I then adopted for 
examining the liver was to remove and weigh it, and then to pass a stream of water 
through its vessels until its tissue was completely deprived of sugar. After a vegetable 
diet, I noticed, first, that the liver was of enormous size, in comparison with what I 
had been accustomed to meet with under an animal diet ; and secondly, that there was 
a remarkable quantity of a material present which much interfered with my analysis, 
and which I subsequently found to be amyloid substance. 
In all the observations that follow, the life of the animal was suddenly destroyed, its 
body then opened, and the liver removed. The liver thus circumstanced immediately 
drained itself, by the contraction of its vessels, of the principal portion of its blood, 
whereby was avoided those differences, as regards degree of congestion, which are 
observable in the human subject, where the examination is not made until some hours 
after death. 
The observations are given without a single exception, just as they presented them- 
selves under their separate heads ; and further, the animals were taken, as they hap- 
pened to be brought to me, without any selection, except such as was needed for the 
vegetable and saccharine diet, many dogs refusing to partake of this kind of food. The 
weights are of the avoirdupois scale. The dogs were weighed just before death, and 
4 K 2 
