THE AREOLAR TISSUE. t 289 



it, except as it surrounds the vessels, two or three removes from 

 the capillaries. 



3. Areolar tissue invests the muscles externally, forming their 

 sheaths or perimysia, which give off prolongations (internal peri- 

 mysia) investing the fasciculi of fibres. The heart, however, con- 

 tains this element in very small proportion, its fibres intertwining 

 in such a manner as to render an extraneous bond of connection 

 unnecessary. It also lies between and underneath the muscles, and 

 in greater quantity in proportion to the required mobility. 



4. This tissue is abundant around internal organs which undergo 

 changes of form, size, or position in the performance of their func- 

 tigns, and which are partially or wholly without a free surface, as 

 the pharynx, oesophagus, bladder, lumbar colon, &c.; and its fila- 

 ments are long, tortuous, and largely intertwined. It also envelops 

 all the glands, and sends prolongations into their interior among 

 their lobules ; it being more abundant in proportion as the gland is 

 less compact, and allowing motion of one part upon another. E. g. 

 it is far more abundant in the mammary gland than in the liver. 



5. Under the skin and the mucous and serous membranes, it 

 forms a distinct layer, though presenting great varieties in respect 

 to quantity and denseness. 



6. Finally, the corium of the skin and of mucous and serous 

 membranes is merely condensed areolar tissue, as will be seen. 



Peculiarities of Areolar Tissue. 



A peculiar form of areolar tissue is said by Henle to exist in 

 company with the arteries at the base of the brain ; the elastic fibres 

 forming rings and spirals around the fasciculi of the white fibrous 

 tissue. 



The subcutaneous areolar tissue is also of peculiar practical im- 

 portance, and will therefore receive some additional notice here. 



The Subcutaneous Areolar Tissue. 



The layer of areolar tissue under the skin was formerly called 

 the cellular membrane. It is properly termed the superficial fascia, 

 or the subcutaneous- areolar tissue. It, singularly enough, is de- 

 scribed by Kolliker as one of the layers of the skin itself; and 

 whenever it contains fat-cells in its areolae, it is by him called the 

 panniculus adiposus. He also restricts the term superficial fascia to 

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