128 
HISTOLOGY OF ANIMALS. 
serous areolar tissue. In the mesentery of small animals, 
the Rabbit for instance, the sub serous layer is repre- 
sented only by a few branched fibres, these form a 
delicate framework over which the serous membrane 
with its epithelium is stretched. In all the situations, 
where it is normally found, it may he developed to 
such an extent as to form tumours, which when sub- 
cutaneous, often attain an enormous size. Most of 
those remarkable growths known as fibrous tumours, 
are composed of this tissue. They often occur in the 
neighbourhood of glandular organs, but specimens 
which have been described as fibrous tumours of the 
breast, are found on minute examination to be chiefly 
composed of hypertrophied glandular tissue, intermixed 
with only so much fibrous tissue as is sufficient to give 
support to the enlarged lobules of the gland. 
When areolar tissue is examined with a power of 
two hundred and fifty diameters, it will be found, as 
before stated, to be composed 
principally of white fibres, the 
yellow or elastic element be- 
ing only occasionally seen. 
In the areolar tissue from 
the pleura of the Elephant 
(Fig. 104) a few yellow 
fibres (b b) are visible, but 
when acetic acid is added to 
a portion of the same tissue, 
a remarkable change takes 
FIG. 104 . 
n- a 
Areolar tissue of the Elephant: 
a a a, white fibres ; h h h, yellow 
elastic fibres. 
