FORMATION OF THE TISSUES AREOLAR TISSUE. 499 



purpose should be altogether discontinued. The tissue in question, now gene- 

 rally designated the Areolar, is found, when examined under the Microscope, 

 to consist of a network of minute fibres and bands, interwoven in every direc- 

 tion, so as to leave innumerable interstices, which communicate with each 

 other. According to Messrs. Todd and Bowman, the two kinds of Fibrous 

 tissue which elsewhere exist separately, the white, and the yellow, may 

 be detected in Areolar tissue. The White presents itself in the form of in- 

 elastic bands, the largest l-500th of an inch in breadth, somewhat wavy in 

 their direction, and marked longitudinally by numerous streaks ; these streaks 

 are rather the indications of a longitudinal creasing than a true separation 

 into component fibres; for it is impossible by any art to tear up the band into 

 filaments of a determinate size, although it manifests a decided tendency to 

 tear lengthways. These bands vary considerably in size ; the smallest re- 

 quiring a good instrument to render them visible. The Yellow fibrous 

 element exists in the form of long, single, elastic, branched filaments, with 

 a dark decided border, and disposed to curl when not put on the stretch. 

 These interlace with the others, but appear to have no continuity of substance 

 with them. They are for the most part between 1 -5000th and l-10,000th of 

 an inch in thickness ; but they are often met with both larger and smaller. 

 The effect of Acetic acid upon these two elements is very different ; the 

 white immediately swells up, and becomes transparent ; whilst the yellow 

 remains unchanged. This agent frequently brings into view certain oval 

 corpuscles, which lie in the midst of the bands and threads, and which some- 

 times appear to have delicate prolongations among them. These are usually 

 supposed to be the persistent nuclei of the cells from which the tissue was 

 developed. According to Henle, the fasciculi or bands are occasionally con- 

 stricted by one or more dark filaments, which wind spirally round them, or 

 encircle them with distinct rings ; these are termed by him nucleus-filaments, 

 from his idea of their origin ( 613).- The interstices of Areolar tissue are. 

 filled during life with a fluid, which resembles very dilute Serum of the blood ; 

 it consists chiefly of water, but contains a sensible quantity of common salt 

 and albumen, and (when concentrated) a trace of alkali sufficient to affect test- 

 paper. The great use of this Tissue appears to be, to connect together organs 

 and parts of organs which require a certain degree of motion upon one another; 

 and to envelop, fix, and protect, the blood-vessels, nerves, and lymphatics, 

 with which these organs are to be supplied. It can scarcely be said to enjoy 

 any vital powers, and is connected solely with physical actions ( 611). It is 

 extensible in all directions, and very elastic, in virtue of the physical arrange- 

 ment of its elements ; and it posesses no contractility beyond that of the vessels 

 which are distributed through it. It cannot be said to be endowed with sen- 

 sibility ; for the nerves which it contains seem to be merely en route to other 

 organs, and not to be distributed to its own elements. And its asserted powers 

 of absorption and secretion appertain rather to the walls of the capillary blood- 

 vessels than to the threads and bands of which it is composed. Areolar tissue 

 yields Gelatin by boiling ; but this is derived from the White fibrous element 

 only ; the yellow not being affected by the process. 



638. The White Fibrous tissue exists alone in Ligaments, Tendons, Fibrous 

 Membranes, Aponeuroses, &c. ; where it presents the same characters as those 

 just described, except that the bands are less wavy, and frequently quite 

 straight, so that it is inextensible. It receives very few blood-vessels, and still 

 fewer nerves ; indeed it would seem that, in many structures (as tendons), it 

 is totally insensible. It seems entirely destitute of any vital property; and 

 its chemical nature is such, that it needs very little interstitial change to main- 

 tain its normal composition. If dried, it has not the least tendency to putrefy ; 

 and when moist, it resists the putrefactive process more strongly than any of 



