76 



LOCOMOTION. 



[CHAP. in. 



ever, where this tissue is in great 

 abundance, and where it first at- 

 tracted attention at the time when 

 elementary tissues began to be se- 

 parately studied, the meshes thus 

 formed are disposed so as to con- 

 stitute secondary cavities, having 

 a somewhat determinate shape 

 and size, and which are visible to 

 the naked eye. These generally 

 contain fat, and may be admirably 

 studied in most parts of the sub- 

 cutaneous tissue. They are better 

 deserving the name of cells than 



Portion of Areolar tissue, inflated and dried, , . _, , , , n 



shewing the general character of its larger meshes, the interstlCCS formed by the first 



Each lamina and filament here represented con- . PIT 



tains numerous smaller ones matted together by interlacement OI the elementary 



the mode of preparation. Magnified twenty dia- _. 



meters. filaments. J3ut they communicate 



freely, as the smaller interstices do, their walls being everywhere 

 cribriform, and capable of giving passage to air or fluids. 



The areolar tissue is one of the most extensively diffused of all 

 the elements of organization, and its chief purpose seems to be that 

 of connecting together other tissues in such a way as to permit a 

 greater or less freedom of motion between them. To do this, it is 

 placed in their interstices, and is more or less lax, more or less 

 abundant, according to the particular exigency of the part. It 

 is by means of this tissue, as well as by the complexity of its own 

 web, that almost every part of the vascular system is fixed in its 

 position, and allowed to undergo the movements impressed upon 

 it by the circulative powers. Even the capillaries supplying this 

 system itself are for the most part brought to it, and enveloped, by 

 this tissue. 



So true and comprehensive is this description of the association 

 of the areolar tissue with the vascular, that it would be difficult to 

 point out a single instance in which one office of the former is 

 not to envelope and protect the latter. But the statements that 

 have been made of its universal presence have no good evidence in 

 their favour. In the compacter parts of bone, in teeth, and in 

 cartilage, it is certainly not present ; and, indeed, it could serve 

 no purpose in those structures. In the substance of the brain, also, 

 it does not exist, excepting around the vessels two or three removes 

 from the capillaries. 



In the muscles it connects the elementary fibres to one another, 



