1086 GENERAL ANATOMY OR HISTOLOGY. 



CONNECTIVE TISSUES. 



The term connective tissue includes a number of tissues which possess this 

 feature in common, viz., that they serve the general purpose in the animal econ- 

 omy of supporting and connecting the tissues of the body. These tissues may 

 differ considerably from each other in appearance, but they present, nevertheless, 

 many points of relationship, and are, moreover, developed from the same layer 

 of the embryo, the mesoblast. They are divided into three great groups : (1) 

 the connective tissues proper, (2) cartilage, and (3) bone. Blood, which has 

 already been described, is, strictly speaking, a form of connective tissue, and is so 

 dealt with by many histologists. 



The Connective Tissues Proper. Several forms or varieties of connective tissue 

 are recognized: (1) Areolar tissue. (2) White fibrous tissue. (3) Yellow elastic 

 tissue. (4) Mucous tissue. (5) Retiform tissue. They are all composed of a homo- 

 geneous matrix, in which are imbedded cells and fibres the latter of two 

 kinds, white and yellow or elastic. The distinction between the different forms 

 of tissue depends upon the relative preponderance of one or other kind of fibre, of 

 cells, or of matrix. 



Areolar tissue (Fig. 610) is so called because its meshes are easily distended, and 

 thus separated into areolse or spaces, which open freely into each other, and are 



Plasma cell. 



.^.White fibres. 



Lamellar cell. 

 FIG. 610. Subcutaneous tissue from a young rabbit. Highly magnified. (Schafer.) 



consequently easily blown up with air, or permeated by fluid when injected into 

 any part of the tissue. Such spaces, however, do not exist in the natural con- 

 dition of the body, but the whole tissue forms one unbroken membrane com- 

 posed of a number of interlacing fibres, variously superimposed. Hence the 

 term " the cellular membrane " is in many parts of the body more appropriate 

 than its more modern equivalent. The chief use of the areolar tissue is to bind 

 parts together, while by the laxity of its fibres and the permeability of its areolse 

 it allows them to move on each other, and affords a ready exit for inflammatory 

 and other effused fluids. It is one of the most extensively distributed of all the 

 tissues. It is found beneath the skin in a continuous layer all over the body, 

 connecting it to the subjacent parts. In the same way it is situated beneath the 

 mucous and serous membranes. It is also found between muscles, vessels, and 



