FEB 
of cordage, and of other substances which 
are employed in the communication of mo- 
tion, where flexibility is required, as well as 
the utility of other flexible materials, de- 
pends principally upon the lateral adhesion 
produced by twisting, or by the intermixture 
of fibres. The mechanism of simple spin- 
ning is easily understood; care is taken, 
where the hand is employed to intermix 
the fibres sufficiently ; and to engage their 
extremities as much as possible in the cen- 
tre ; for if any fibre were wholly external 
to the rest, it could not be retained in the 
yarn. See Rope, Spinning, &c. 
FIBRIN. If a quantity of blood, newly 
drawn from an animal, be allowed to re- 
main at rest for some time, a thick red clot 
gradually forms in it, and subsides. Sepa- 
rate this clot from the rest of the blood, 
pot it into a linen cloth, and wash it re- 
peatedly in water till it ceases to give out 
any colour or taste to the liquid ; the sub- 
stance which remains after this process is 
denominated fibrin. It has been long 
known to physicians under the name of the 
fibrous part of the blood ; but has not till 
lately been accurately described. It may 
be procured also from the muscles of animals. 
Fibrin is of a white colour, has no taste 
nor smell, and is not soluble in water nor in 
alcohol. It undergoes no change, though 
kept exposed to the action of the air; nei- 
ther does it alter speedily, though kept co- 
vered with water. When exposed to heat, 
it contracts very suddenly, and moves like 
a bit of horn, exhaling at the same time the 
smell of burning feathers. In a stronger 
heat it melts. When exposed to destruc- 
tive distillation, it yields water, carbonate 
of ammonia, a thick, heavy, fetid oil, traces 
of acetic acid, carbonic acid, and carbureted 
hydrogen gas. The charcoal, as Hatchett 
ascertained, is more copious than that left 
by gelatine or albumen. It is very difficult 
to incinerate, owing to the presence of 
phosphate of soda, and some phosphate of 
lime, which form a glassy coat on the sur- 
face. A considerable proportion of carbo- 
nate of lime also remains after the incine- 
ration of the charcoal. 
Acids dissolve fibrin with considerable 
facility. Sulphuric acid gives-it a deep 
brown colour; charcoal is precipitated, and 
acetic acid formed. Muriatic acid dissolves 
it, and forms with it a green-coloured jelly. 
The acetic, citric, oxalic, and tartaric acids, 
also dissolve it by the assistance of heat ; 
and the solutions, when concentrated, as- 
sume the appearance of jelly. Alkalies 
FIB 
precipitate the fibrin from acids in flakes, 
soluble in hot water, and resembling gela- 
tine in its properties. 
From the recent experiments of Fourcroy 
and Vauquelin, on the muscular fibres of 
animals, there can be little doubt that fibrin, 
when treated with hot nitric acid, under- 
goes a suit of changes. 1. It is converted 
into a yellow matter, which still possesses 
the fibrous texture of fibrin. It has the 
property of converting vegetable blues to 
red, has a bitter taste, is but little soluble 
in water, and is insoluble in alcohol. It 
combines with alkalies, decomposes their 
carbonates, unites to oils, and gives them 
rancidity and acid properties. To this 
snbstance, Fourcroy and Vauquelin have 
given the name of yellow acid. 2. By the 
farther action of the nitric acid, this yellow 
matter becomes more soluble, acquires a 
reddish tinge, and seems to become soluble 
in alcohol. 3. The last state into which it is 
brought by nitric acid seems to be that spe- 
cies of bitter principle which crystallizes and 
detonates when combined with ammonia. 
The alkalies, when diluted, have but little 
effect upon fibrin ; but when concentrated 
potash or soda is boiled upon it, a complete 
solution is obtained of a deep brown colour, 
possessing the properties of soap. During 
the solution ammonia is disengaged. When 
the solution is saturated with muriatic acid, 
a precipitate is obtained similar to that from 
animal soap, except that it sooner becomes 
hard and soapy when exposed to the air. 
The earths, as far as is known, have little 
or no action on fibrin. Neither has the 
action of the metallic oxides and salts been 
examined. Fibrin is insoluble in alcohol, 
ether, and oils. The effect of other re- 
agents on it has not been examined. 
FIBROLITE, a species of the topaz 
family, first observed by Bournon in the 
matrix of the imperfect corundum. Colour 
white, or dirty grey ; hardness rather 
greater than that of quartz ; specific gravity 
3.214; texture fibrous ; cross fracture com- 
pact; internal lustre glossy; infusible by 
the blowpipe; usually in shapeless frag- 
ments. Bournon observed one specimen 
crystallized, in a rhomboidal prism ; the 
angles of whose faces where 80° and 100". 
It is composed, according to Chenevix, of 
52.25 alumina, 38 00 silica, and 3.75 a trace 
of iron and loss. 
FIBULA, in anatomy, a long bone placed 
on the outside of the leg, opposite to the 
external angle of the tibia. See Ana- 
tomy. 
