60 PHILOSOPHY OF ZOOLOGY. 
readily, especially when assisted by heat. It is insoluble in 
alcohol. 
Dr Tomson found that a concentrated solution of gela- 
tine, yielded, with nitro-muriate of gold, a copious yellow- 
ish-white precipitate, soluble by adding water ; and, with ni- 
trate of mercury, a very copious curdy precipitate. 
When a solution of tannin is dropt into a solution of ge- 
latine, an union takes place, and an insoluble precipitate, 
of a whitish colour, falls to the bottom. It is on the 
union of the tannin of the oak bark with the gelatine of the 
hides, that the process of tanning leather depends. 
When exposed to the destructive distillation, it yields a 
watery liquor, impregnated with ammonia, a fetid oil, and 
a bulky charcoal, which, by incineration, gives obvious 
traces of phosphate of lime, and phosphate of soda. It 
consists of carbon, hydrogen, oxygen, and azote, in propor- 
tions which have not been satisfactorily determined. 
Gelatine exists in abundance in the different parts of ani- 
mals, as bones, muscles, skin, ligaments, membranes, and 
blood. It is obtained from these substances, by boiling 
them in warm water; removing the impurities, by skim- 
ming, as they rise to the surface; or by subsequent strain- 
ing and clarifying. It is then boiled to a proper consis- 
tency. It is the characteristic ingredient of the softest and 
most flexible parts of animals. 
It is extensively used in the arts, under the names Glue 
and Size, on account of its adhesive quality, and to give 
the requisite stiffness to certain articles of manufacture. In 
domestic economy, it is likewise employed in the form of 
jelly, and in the formation of various kinds of soup. What 
is termed Portable Soup is merely jelly, which has been 
dried, having been previously seasoned, according to the 
taste, with different spices. 
2. Albumen.—This substance derives its name from the 
Latin term for the white of an egg, that liquid bemg con- 
