The chemical composition of this substance has been frequently examined, but it is only within a comparatively recent period that correct ideas have been entertained respecting it. Thus Haller thought that the cellular fibre was formed of earthy particles which are held together by an intermediate glue or cement composed of oil combined with water. The discoveries of modern chemistry have disproved this theory, by showing that earth is not such an essential constituent of membrane as was formerly supposed, and also that the particles which compose the cellular tissue, or any other solid, are held together by a vital attraction, and not by any particular connecting medium. We are indebted to the French chemists for more correct information concerning the nature of the animal compounds. Fourcroy, finding that a large quantity of jelly could be extracted by boiling from many membranous bodies, was disposed to regard membrane as essentially composed of jelly. He states that the cellular texture, and other parts which resemble it in their chemical composition, as tendons, ligaments, Sec., are entirely dissolved in boiling water, and form with it, while it remains hot, a viscous fluid, which, when cold, concretes into a transparent and tremulous jelly. This statement is erroneous in two respects; in the first place, there is probably no single article of these enumerated by Fourcroy, which is completely soluble in water when boiling under the ordinary atmospheric pressure; and, secondly, although jelly, in a greater or less proportion, may probably be procured from all of them, yet they differ very much in the quantity which they contain. We learn, from the experiments of Mr. Hatcher, that condensed or coagulated albumen forms the basis of membranous matter; but it also probably contains some jelly, especially in young animals in which this substance forms so large a proportion of the body. Another substance, according to Dr. Bostock, enters into the constitution of membrane, or at least is frequently connected with it, viz. animal mucus. This appears to be nearly related to albumen, and is probably a mere modification of it. A large quantity of water is contained, as in all other parts, in the cellular issue. When deprived of this by desiccation, the texture loses some of its physical properties, and acquires new ones. According to Bichat, it remains white; the cells adhere together, and the laminae, which were spread out for the purpose of drying, have the appearance of a serous membrane. When it is again placed in water, it regains, although in an imperfect manner, its former aspect. Exposed to a red heat, it dries rapidly, becomes crisp, and ends by burning. It resists putrefaction for a long period, so that it requires to be kept for months in water before decomposition is effected. It is at length converted into a viscous substance resembling muria. This resistance to decomposing agents, appears, in part at least, to depend on the degree of density which the membrane possesses; thus ligaments remain unaltered longer than the common cellular tissue. Membranous matter is soluble in the mineral acids, with the assistance of heat. It is also dissolved in the pure fixed alkalis. With respect to the ultimate chemical elements, it seems that the cellular tissue consists of oxygen, hydrogen, carbon, and azote. The last named substance is found in a smaller proportion than in some other animal bodies, and it is probably owing to this circumstance, that membrane is capable of resisting for so long a time, the influence of putrefaction. <Callout type="important" title="Key Insight">Understanding the composition helps in recognizing signs of decomposition or spoilage.</Callout> The properties and uses of the cellular tissue are of great importance, in consequence of the influence they exert on the actions of the other organs of the body. The physical qualities, such as cohesion, flexibility, extensibility, and elasticity, are much more strongly marked than the vital ones of contractility and sensibility; indeed there is reason to doubt if the two latter are ever developed in the cellular substance, at least while it continues in a state of health. The cohesive ness of this structure, which is one of its essential properties, varies according to the nature and situation of the organs with which it is connected; thus, in some phures, its cohesion scarcely exceeds that of a viscid fluid, while in other parts its resistance is so great that it cannot be overcome except by considerable force. Flexibility and a certain degree of extensibility are also necessary; for if the cellular membrane was unyielding, the movements of the body could not be performed, or only at the expense of great muscular exertion. The elasticity of reticular matter is decidedly its most important property, as we may refer to it all those phenomena which have been supposed by some writers, especially by Bichat, to result from contractility. This celebrated physiologist ascribes the contraction of the rectum on exposure to cold, to the contractility of its cellular structure, and although he says that this contraction is not to be compared to that of the muscles, yet, he conceives, that the two operations differ from each other in degree only, and not in kind. The preceding phenomenon may be more correctly explained by supposing that the cremaster is the principal cause of it, and that the application of cold, by corrugating the rectum, assists in producing the appearance that has been noticed. Blumenbach describes the contractility which is observed in membrane after it has been over distended by the name of vis cellulosa; this term, however, does not imply the same kind of contraction as that of the muscles. He adduces, as an example of the vis celluloa, the action of the cellular membrane in propelling the serous exhalation into the lymphatic vessels. Bichat has also attributed to the same kind of power, which he calls insensible organic contractility, the exhalation and absorption of the cellular texture. It is probable that all the phenomena which have been brought forward by the above physiologists in support of their opinions, may be accounted for by the elastic property which is so greatly developed in this structure, and by its power of imbibition. The question concerning the sensibility of membrane has given rise to much discussion among anatomists. It has been judiciously remarked by Hildt that many of the errors which have prevailed upon this subject have been caused by the most distinguished authors confounding together under the same denomination, the nerves, the tendons, and the ligaments. This erroneous opinion was derived from Hippocrates, who decided that tendinous and membranous parts are among the most sensitive organs of the body. We may conclude from the investigations of Holler, Whytt, and others, that the cellular texture in its natural condition is insensible; but that when it is inflamed, it becomes extremely painful. In the latter state it is difficult to determine whether the pain should be referred to the sensibility of the cellular tissue or to the distension of the nervous branches which traverse it in order to reach the surrounding structures. The cellular tissue is the seat of a very active process of secretion and absorption. In health, these two operations are equal to each other, so that no accumulation occurs; but as soon as the equilibrium is destroyed, the fluids distend the cells and grow to the most depending porta. The secreted liquid which has a great resemblance to that derived from the serous membranes appears to fulfil a similar office in the animal economy; that is to say, it facilitates the motions of the various organs, in consequence of lubricating the delicate parts of the cellular tissue. <Callout type="important" title="Insight on Secretion and Absorption">Understanding these processes can help in managing fluid balance during survival situations.</Callout> • I have alluded, in another part of this chapter, to the opposite opinions that produced with respect to the mechanism by which these processes are effected. Until very lately, anatomists believed, that secretion was accomplished by certain minute arteries called exhalants and absorption, by the agency of the lymphatic vessels. The experiments that have been performed by M. M. Magendie and Fodru tend to disprove the existence of these exhaling and inhaling tubes. The latter of these physiologists draws the following conclusions from his investigations: 1. That exhalation and absorption are respectively effected by transudation and imbibition, and depend on the capillarity of the tissues. 2. That this double phenomenon may take place in all parts of the body, and that the liquids with which they are imbided, may be equally carried by the lymphatic vessels, or by the arteries and veins.* The experiments by which these opinions are supported, merit great attention, in consequence of their importance; but although they have determined many new and interesting facts, the question concerning the exact mechanism of exhalation and absorption must still be considered as veiled in obscurity. <Callout type="risk" title="Risk of Misinterpretation">Incorrectly interpreting these processes can lead to ineffective fluid management.</Callout> The adipose tissue ought to be regarded as a distinct modification of the cellular membrane, because the cells in which the fat is lodged do not communicate with those which contain the lymph or serosity. This distinction between the two tissues was first observed by Dr. W. Hunter, who thought that there was a particular organization or glandular apparatus superadded to the reticular membrane, consisting of vesicles for lodging the animal oil, and of vessels fitted for its secretion.* These bags, which are distinct from those containing the air in emphysema, or the water in anasarca, he calls adipose cells, in opposition to the general ones, which he calls reticulated. This opinion, which has been adopted by Prochaska, Mascagni, Chaussier, and Gordon, has been supported, with great ability, by Beclard. The distinct existence of the adipose tissue was denied by Haller, and afterwards by Bichat and Meckel. In investigating the nature of the adipose cells, I shall endeavour to show that the opinion of Haller is not correct; for although these vesicles are seldom, if ever, met with unaccompanied by cellular substance, yet that circumstance does not establish their identity. <Callout type="warning" title="Potential Misidentification">Misidentifying adipose tissue can lead to incorrect treatment.</Callout> The forms of adipose tissue will be described in the next section.
Key Takeaways
- Membranes are composed of water, albumen, and possibly mucus.
- The cellular tissue's elasticity is crucial for bodily functions.
- Secretion and absorption processes can be managed by understanding their mechanisms.
Practical Tips
- Understand the composition of membranes to identify signs of spoilage or decomposition in survival situations.
- Recognize that the cellular tissue's insensitivity under normal conditions can change during inflammation, indicating potential health issues.
- Manage fluid balance by understanding the processes of secretion and absorption.
Warnings & Risks
- Misinterpreting the mechanisms of exhalation and absorption can lead to ineffective fluid management in survival scenarios.
- Incorrectly identifying adipose tissue can result in improper treatment or misdiagnosis.
Modern Application
While the specific chemical composition discussed may not be as relevant today, understanding the properties and functions of cellular tissues is crucial for managing injuries, infections, and maintaining overall health during survival situations. The principles of fluid balance and the importance of elasticity in tissue function remain applicable.
Frequently Asked Questions
Q: What are the key components of membrane composition according to Haller's theory?
According to Haller's theory, the cellular fibre was formed of earthy particles held together by an intermediate glue or cement composed of oil combined with water.
Q: How does modern chemistry disprove Haller's theory about membrane composition?
Modern chemistry disproves Haller's theory by showing that earth is not a significant constituent of membranes, and the particles composing cellular tissue are held together by vital attraction rather than any particular connecting medium.
Q: What does Bichat state about the properties of cellular tissue?
Bichat states that the cohesive ness of cellular structure varies according to its nature and situation, and it is marked by physical qualities such as cohesion, flexibility, extensibility, and elasticity.