AREOLAR TISSUE. Wig 
cell. Last of all, the nucleus also disappears, and fibrils alone 
remain. All these transformations proceed in a homogeneous 
eytoblastema, which probably also continues to exist between 
the fibres of areolar tissue in the adult. 
b. Adipose cells. In the later periods of foetal existence, 
adipose cells occur in many situations in addition to the fibre- 
cells before described. They are usually first seen in small 
groups between the fibre-cells. They are round cells of very 
various sizes, which are generally completely filled by a single 
fat-globule. The cell-membrane which closely encompasses 
the contents, is most minutely granulous, or, according to 
Gurlt, homogeneous. It is in most instances very thin, being 
about half the thickness of a blood-corpuscle, but sometimes it 
is much thicker, and in the subcutaneous areolar tissue of the 
thigh of a rickety child, at the age of twelve months (probably 
in connexion with the disease), was almost as thick as the 
breadth of a human blood-corpuscle. In the early stage, this 
cell-membrane encloses a very distinct nucleus of a round or 
oval form, which is sometimes flattened. When the former is 
thin, the nucleus presents itself externally as a little promi- 
nence upon the round fat-globule, which is closely encom- 
passed by the cell-membrane ; but when thick, the nucleus lies 
embedded in it. It contains one or two nucleoli. It is not 
uncommon for adipose cells to contain a number of small 
globules instead of one fat-globule, in such instances, one of 
them is generally remarkable for its larger size. The adipose 
cells are best seen in the fat found in the cranial cavity of a 
young carp, before it has attained the length of six inches. 
(See pl. III. fig. 10.) They there lie in so soft a substance, 
that they may be insulated without any difficulty, and float 
singly in the water in which they are examined. Some are so 
large as to be visible even with the unaided eye. When 
examined under the microscope with a magnifying power 
of 450, the cell-membrane is readily recognized, it is very 
thin, and closely encompasses the contents. It rises into 
a little prominence on one side, within lies a proportion- 
ately large, and very beautiful cell-nucleus, which is oval, 
but not flattened, and contains one or two very distinct 
nucleoli. Some of these fat-cells have two such nuclei, which 
