in their Strticture and Functions* ^ 389 



insensible and incontractile. Its ultimate chemical elements 

 appear to be oxygen, hydrogen, and carbon. 



In animals we perceive the same extensive diffusion of 

 the membranous tissue as we find occurring in plants. Mem- 

 brane forms the principal ingredient of every part belonging 

 to the animal frame, and exceeds in quantity all the other 

 structures of the body taken together. It not only affords a 

 complete envelope to the exterior of the body, but it covers 

 the whole of its internal surfaces. It forms the solid part of 

 all the viscera, it covers every individual organ, and lines 

 every cavity in which the organs are contained. It com- 

 poses the chief bulk of the bones, and enters largely into the 

 composition of the muscles. It constitutes nearly the whole 

 mass of the tendons, the ligaments, and the cartilages. It 

 composes the cellular texture, and is the chief ingredient in 

 the structure of the glands. It envelopes the brain, the 

 spinal cord, and all the nerves. It composes almost entirely 

 such organs as the stomach, the intestines, and the bladder ; 

 and it forms the principal part of the tubes and vessels, whose 

 office is to convey the fluids to every part of the animal 

 system. According to Haller, animal membrane is com^ 

 posed of a vast assemblage of small and extremely delicate 

 fibres. Its ultimate elements consist of oxygen, hydrogen, 

 carbon, and azote. The tardiness, however, with which it 

 undergoes the putrefactive fermentation, indicates that its 

 proportion of azote must be exceedingly minute. Animal 

 membrane, like that of vegetables, is possessed only of phy- 

 sical properties ; it exhibits cohesion, flexibility, extensibilityj 

 and elasticity, but it is totally incapable of spontaneous con-r 

 traction, and is likewise devoid of all sensibility. It therefore 

 appears, that animal membrane is not only the most abundi- 

 ant, but the most simple, of all the organised parts of the 

 body ; andj that in its chemical composition, in its mechanic 

 cal structure, its universal diffusion, and its uninterrupted 

 continuity, in its being endued only with physical properties 

 and in its wanting those which are vital, it bears a most 

 striking resemblance to the membranous matter of plants. 



If we cut fi-om the stem of a plant a thin transverse slice, 

 and carefully examine it by means of a microscope, we shall 

 find that it is composed of a number of minute cells. This 

 structure constitutes what is termed the cellular tissue. It is 

 formed entirely of membranous matter, and possesses the same 

 properties. It enters, as a component, into the structure of 

 almost all the vegetable organs ; it likewise envelopes them, 

 and connects their several parts together. The cells of the 

 cellular tissue seem in most instances to communicate with 



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