do not possess corresponding veins. It has, however, been ascertained by M. Dupuytren that there are proper veins of the osseous tissue, which pass from the interior by openings, in which no arterial ramifications can be perceived, even after the most successful injection; they are composed only of the internal membrane of the venous system, which is folded into numerous valves. <Callout type="important" title="Important">Lymphatic vessels have not been seen in the interior of the bones but may be distinguished on the outer surface of the large ones.</Callout> Their existence cannot be doubted as we have constantly proved their action in caries and necrosis, and in the rare affection called mollities ossium. The experiment of feeding an animal on madder exemplifies, in a striking manner, the activity of reticulo-venous deposition, and also of lymphatic absorption. It is well known that, after the use of this substance for a short time, the bones assume a red tinge, in consequence of its colouring matter being secreted from the <Callout type="gear" title="Gear">arteries.</Callout> Now, if the use of the madder be discontinued for some time before the animal is killed, it will be found, on examining the bones, that they have resumed their natural colour, a change which could have happened only by the action of absorption. The nerves which enter the bones accompany the medullary artery; they are very minute, and according to Richerand, form a plexus around the vessels. Some authors thought that these nervous threads were merely destined for the blood-vessels, whilst others contend that they supply the medullary membrane. The existence of nerves in the substance of bone is, however, generally, and I believe correctly, admitted; the most direct evidence in support of this opinion is deduced from the fact that bones become painful when they are inflamed. Every bone is covered externally by a dense structure called the periosteum, and internally it is provided with a delicate production known by the name of the medullary membrane. The periosteum has been described in the chapter on the fibrous organs. See page 351. <Callout type="risk" title="Risk">The medullary membrane consists of an extremely delicate process of the cellular tissue, which can be demonstrated by showing a bone and plunging it in an acid, when the membrane is detached in the form of a distinct canal.</Callout> The fluid secreted by the medullary blood-vessels is known by the general name of marrow; it is principally contained in the centre of the long bones, but some part is lodged in the spongy substance, where it is often called medullary fluid. The compact tissue also contains an oily juice, which is probably contained in the longitudinal canals already mentioned; it is, according to some writers, of a thinner consistence than marrow and has been termed, to distinguish it, oil of bones. <Callout type="tip" title="Tip">The marrow does not exist in the fetus nor in the young subject; although the membrane is seen when the bone is hollowed into a canal by the progress of ossification, but it contains at the beginning merely a viscid and gelatinous fluid.</Callout> In old age, the interior of the bones being hollowed by a progressive absorption of the osseous matter, the marrow accumulates in quantity. There is much uncertainty concerning the use of the medullary fluids. The most distinguished authorities of the day, such as Boerhaave and Haller, thought that the marrow served to render the bones less brittle, and this opinion has even been adopted more lately by Blumenbach and others. But there is no doubt that the flexibility of the bones depends on the animal substance they contain, and not on the marrow; it is for this reason that the bones of young persons, which have little or none of the latter substance, are more yielding and less fragile than those of old people, in which the marrow is greatly accumulated. The real uses of this fluid are in all probability the same as those of the fat in other parts of the body; but in addition it serves to make the bones lighter in consequence of its low specific gravity. <Callout type="warning" title="Warning">The process of ossification has been for a long time the subject of much speculation among physiologists, and the numerous experiments and observations which were made by the older anatomists have shown that the only peculiarity in the growth of bone is the deposition of a certain quantity of earthy substance in the animal mould which is destined to receive it.</Callout> In other respects, there is no deviation from those general laws which go the development of the other parts of the animal body. The bones are distinguished from all other parts of the body by their great solidity and durability, which qualities depend on the calcareous substance they contain. Many anatomists speak of their elasticity; but this property is very inconsiderable, or indeed entirely deficient, except in the beginning of life. Bones are endowed with a certain degree of extensibility, so that they may yield to a distending force, which is gradually applied; this is seen when tumours of various kinds are formed in the interior of osseous cavities, as in the maxillary sinuses, the nostrils, and orbits. After being extended, they are capable of contracting themselves, but in a very slight degree. These organs have a yellowish white colour, the tinge being generally deeper in the advance of age. During life they have a dark reddish brown or purple colour owing to the quantity of blood they contain. Although the bones do not exhibit any of the striking phenomena which are regarded as the distinctly characteristic features of life, we must not therefore conclude that they are deprived of vitality. The observations which have been offered in the preceding pages of this chapter sufficiently prove that the bones are nourished and renovated like the other parts of the body; and the processes that occur in the various accidents and diseases to which they are liable, still more forcibly demonstrate that they are endowed with the living principle. They are not sensible in their healthy condition, but become so during inflammation, so that they are then extremely painful.
Key Takeaways
- Bones contain a medullary membrane and marrow which play crucial roles in their development and maintenance.
- The process of ossification involves the deposition of earthy substance into an animal mould, similar to other parts of the body's growth processes.
- Bones are vital for supporting and protecting softer tissues and organs within the body.
Practical Tips
- Understand that bones have a certain degree of extensibility which can help in some survival scenarios where force is applied gradually.
- Recognize the importance of marrow in bone health, especially during growth and aging stages.
- Be aware of the role of the periosteum in protecting and nourishing bones.
Warnings & Risks
- Do not assume that bones are entirely inflexible; they can yield to certain forces which could be useful or harmful depending on the situation.
- Avoid applying excessive force to bones, as this can lead to fractures or other injuries.
- Be cautious of infections in bone tissue, as inflammation can cause significant pain and may require medical attention.
Modern Application
While the specific techniques for treating bone injuries have evolved significantly since 1829, understanding the basic anatomy and processes involved remains crucial. This knowledge helps in recognizing signs of injury, providing initial care, and knowing when professional medical assistance is necessary.
Frequently Asked Questions
Q: What are the main components of bones according to this chapter?
Bones contain an animal substance (condensed albumen), earthy substances like phosphate of lime, carbonate of lime, and other minerals. They also have a medullary membrane and marrow.
Q: How does ossification occur in the body?
Ossification involves the deposition of a certain quantity of earthy substance into an animal mould that is destined to receive it. This process follows general developmental laws similar to other parts of the body.
Q: What are the functions of bones mentioned in this chapter?
Bones provide support and protection for softer tissues, determine the stature and form of the body, and serve as attachment points for muscles, forming part of the motion apparatus.