CELLULAR TISSUE. 



510 



the substance of the absorbent and secreting 

 glands, investing their several component parts. 



Structure and organization. If a portion of 

 cellular tissue void of adipose substance be ex- 

 amined with the naked eye, and for this purpose 

 that which intervenes between very recent muscu- 

 lar fibres may be advantageously selected, it will 

 be seen that it is composed of an immense num- 

 ber of delicate and semi-transparent filaments, 

 having very much the appearance of the finest 

 threads of a spider's web. These fibrils cross 

 each other in various directions, and in this 

 manner intercept innumerable spaces, which 

 communicate one with another, and exhibit a 

 vast variety of figures. The small spaces or 

 areolae which are thus produced constitute what 

 are called the cells of this tissue ; but as there 

 is nothing determinate either in their size or 

 shape, which evidently vary according to ihe 

 degree of traction exercised in separating the 

 filaments ; as they communicate together, and 

 consequently are not circumscribed ; as they 

 are in fact simply the interstices left between 

 the fibres, the expression in common use is 

 calculated to convey an erroneous idea of the 

 real nature of these spaces. 



If the investigation be prosecuted with the 

 aid of a powerful microscope, a very beautiful 

 appearance will be presented, of which it is 

 impossible to convey an adequate idea by any 

 description. We shall still observe fibres cross- 

 ing in all directions ; but although I have had 

 many favourable opportunities of making these 

 observations, I have never been able to detect 

 in the cellular fibre that linear arrangement of 

 globules described by Dr. Milne Edwards, and 

 which has of late years been very generally 

 supposed to pervade all the elementary fibres of 

 the body. A number of globular particles may, 

 it is true, be seen at irregular distances, either 

 clustered together or dispersed in an isolated 

 manner, but they do not enter into the forma- 

 tion of the fibre. The results, then, of careful 

 inspection disprove the ideas of former anato- 

 mists, some of whom, Ruysch and Mascagni 

 for example, supposed that the cellular fibre 

 was entirely vascular, whilst others imagined 

 it to be an expansion of the nerves : it is now 

 generally admitted that the basis of the cel- 

 lular substance is a solid and elementary fibre; 

 and although to the naked eye it often presents 

 a membranous form, yet microscopical observa- 

 tion evinces that the plates of membrane are 

 distinctly composed of solid fibres. The in- 

 terstices or cells always contain in health a 

 very thin albuminous fluid, which has a great 

 resemblance to the secretion of the serous mem- 

 branes, and also to the serum of the blood ; 

 and hence it is often termed the cellular serositi/. 

 This fluid, which must be regarded as an in- 

 tegrant part of this tissue, has a great influence 

 on its properties, so that if it be entirely re- 

 moved, as by desiccation, the membrane be- 

 comes hard and brittle, and its elasticity is 

 almost lost ; or if it be accumulated in excess, 

 as we often see it in disease, the elastic force is 

 also destroyed. 



'Bloodvessels and lymphatics. An inquiry 

 into the relations which exist between the cel- 



lular and vascular tissues, would lead to the 

 important question, how far vascularity is essen- 

 tial to organization ? Without entering into 

 this investigation, it may be remarked that the 

 cellular substance is provided with blood- 

 vessels; and although the greater number of 

 these merely traverse the membrane in order to 

 reach other parts, yet the phenomena of nutri- 

 tion and absorption shew that a vascular appa- 

 ratus must exist in connexion with the cellular 

 tissue. 



Nerves. It is impossible to trace any ner- 

 vous filaments to the cellular fibres, although 

 such threads may be seen passing between them 

 to the neighbouring organs. The insensibility 

 in its healthy state also seems to indicate the 

 absence of nerves; but as pain is experienced 

 during inflammation, we must admit the ex- 

 istence of some communication with the senso- 

 rium. 



Chemical composition. The cellular sub- 

 stance contains, like all the soft solids of the 

 body, a large quantity of water: when this is 

 evaporated, the fibres and cells adhere to each 

 other, and present a membranous appearance. 

 Analysis shews that albumen and gelatine com- 

 pose this substance ; the former predominating, 

 and being in a state of coagulation, bestows 

 on it the necessary degree of firmness and re- 

 sistance. 



Properties. As we shall have occasion m 

 a future article (see MEMBRANE) to consider 

 this subject more minutely, it will suffice if we 

 here remark that the most important property 

 of the cellular substance is a species of contrac- 

 tion which produces in all the soft parts a con- 

 stant state of tension or tone, which is one of 

 the most remarkable qualities of living bodies. 

 The cause of this peculiar condition, in what- 

 ever part it is evinced, in the skin, in the 

 cellular tissue, in the muscles, in the vessels, 

 &c. is the result of a property inherent in mem- 

 branous matter, which some authorities refer to 

 muscular contractility, and others to elasticity ; 

 whilst many eminent physiologists, denying 

 both these hypotheses, conceive that the con- 

 traction to which we are alluding is of a 

 character sui generis, and which they have 

 called tonicity, vis cellulosa, tonic contraction, 

 contractility of tissue, &c. I confess that none of 

 these theories have ever been to me satisfactory; 

 because, as regards the first, there is no resem- 

 blance between the phenomena connected with 

 the contraction of membranous parts, and those 

 of muscular contraction ; whilst, as respects the 

 second, the resiliency by which the skin re- 

 covers itself after pressure has been made on 

 the external surface, and the retraction and 

 separation of the sides of an incision inflicted 

 on the integument, being observed only during 

 life, and never after death, prove that the results 

 of cellular contraction are, in some important 

 respects, different from those of common elas- 

 ticity. Those writers who, in consequence of 

 the difficulty of referring the phenomena under 

 consideration to either of the known causes of 

 contraction, viz., muscular contractility and 

 elasticity, have imagined the existence of a new 

 kind of contractile power, have, without ad- 



