2 GENERAL COXSIDERATIOXS Ox\ THE TEXTURES. 



some are found in nearly every orjijan ; such is the case with the con- 

 nective tissue, which serves as a binding material to hold together the 

 other tissues Avhich go to form an organ ; the vessels, which convey 

 fluids for the nutrition of the other textures, and the nerves, which 

 establish a mutual dependence among different organs, imparting to 

 them sensibility, and governing their movements. These were named 

 by Bichat the "^" general systems." Others again, as the cartilaginous 

 and osseous, being confined to a limited number or to a particular class 

 of organs, he named " particular systems." Lastly, there are some 

 tissues of such limited occurrence that it has appeared more convenient 

 to leave them out of the general enumeration altogether, and to defer 

 the consideration of them until the particular organs in which they 

 are found come to be treated of Accordingly, the tissues peculiar to 

 the crystalline lens, the teeth, and some other parts, though equally 

 independent textures with those above enumerated, are for the reason 

 assigned not to be described in this part of the work. 



Structural Elements. — It is further to be observed, that the 

 anatomical constituents of the body above enumerated are by no means 

 to be regarded as simple structural elements ; on the contrary, many of 

 them are complex in constitution, being made up of several more 

 simple tissues. The blood-vessels, for instance, are composed of several 

 coats of different structure, and some of these coats consist of more 

 than one tissue. They are properly rather organs than textures, although 

 they are here included with the latter in order that their general 

 structure and properties may be considered apart from their local distri- 

 bution ; but indeed it may be remarked, that the distinction between 

 textures and organs has not in general been strictly attended to by 

 anatomists. The same remark applies to mucous membrane and the 

 tissue of the glands, which structures, as commonly understood, are 

 highly complex. Were we to separate every tissue into the simplest 

 parts which possess assignable form, we should resolve the whole into 

 a very few constructive elements. 



PHYSICAL PROPERTIES. 



The animal tissues, like other forms of matter, are endowed with 

 various physical properties, such as consistency, density, colour, and 

 the like. Of these the most interesting to the ])hysiologist is the pro- 

 perty of imbil)iiig fluids, and of permitting fluids to i)as6 through their 

 substance, which is essentially connected with some of the most im- 

 portant phenomena that occur in the living body, and seems indeed to 

 be indispensable for the maintenance and manifestation of life. 



All the soft tissues contain M-ater. some of them more tlian four-fifths of their 

 weight : this they lose by drying, and with it their softness and flexibility, and 

 so shrink up into smaller bulk and become hard, brittle, and transparent : but 

 when the dried tissue is placed in contact with water, it greedily imbibes the 

 fluid again, and recovers its foi-mer size, weight, and mechanical properties. 

 The imbibed water is no doubt partly contained mechanicallj' in the interstices of 

 the tissue, and retained there by cajnllary attraction, like water in moist sand- 

 stone or other inorganic porous substances ; but the essential part of the process 

 of imbibition by an animal tissue is not to be ascribed to mere porosity, for the 

 fluid is not merely lodged between the fibres or laminaj. or in the cavities of the 

 texture ; a part, i)robably the chief part, is incorporated with the matter which 



