The cause of ossification and the parts which are concerned in that process were till a late period but little known, and even at the present day our information on these subjects is imperfect. It is not, however, my intention to enter into the details of the various theories which have successively occupied the attention of physiologists. I shall confine myself to alluding to a few of the most celebrated doctrines which have advanced to explain the phenomena of ossification.
The anatomists who were contemporaries of Daventie supposed that bone was formed of an osseous juice, which, passing through the conditions of a thin and transparent cartilage, and of a sod and flexible bone, became at last, by a slow coagulation, a firm, hard, and perfect bone. According to this opinion, the production of bone depended more on the mechanical hardening the exuded fluid than on the action of the blood-vessels.
The theory of Duhamel was more plausible, and being founded on an extended series of experiments, it was very generally admitted. This ingenious naturalist contended that the bones are formed by successive layers deposited from the periosteum in the same manner as the rings of wood which are seen in the trunk of a tree are deposited from the inner bark; and he supported this opinion by the effects which he observed from feeding animals on madder. It is known that the colouring principle of this substance, owing to an affinity that exists between it and the phosphate of lime, tinges the bones of a red colour while the soft parts remain unchanged. Now Duhamel asserted that by giving madder to a young animal for a time, suspending its use, and then beginning again to give it, he found on examining the bones that they exhibited alternate layers of a red and white colour which layers he thought corresponded to the periods when the madder was given or withheld. From these experiments he concluded that the bones are formed of concentric laminae which are deposited from the periosteum.
Mr. John Bell has pointed out, in the forcible and expressive manner for which he was so justly celebrated, the contradictions and inconsistencies of Duhamel's theory. But while we admit the general truth of this criticism, it must be recollected that the investigations of Mr. Howship and of Beclard prove that, in certain stages and forms of ossification, the bony matter is undoubtedly secreted from the vessels of the periosteum; and Mr. C. Bell even states that in his museum there was the bone of a pig in which three separate layers could be distinguished by their colour.
The hypothesis of Duhamel was controverted by Haller, who concluded that the bone was formed by its internal vessels altogether independently of the periosteum. This account is much nearer the truth than the former; but still as we have shown in the previous description of ossification it is not free from error.
Some modern writers seem to think that the phenomena which occur in the growth of bone are more inexplicable and mysterious than those which attend the formation of other organs of the body. Thus it has been asked what is the origin of the phosphate of lime? What cause determines it to pass into those particular arteries which go to the bones? And how is it separated in the minute vessels from the other parts of the blood? Is it, as some authors have contended, poured out from the ends of the small arteries; or is it deposited from pores placed on their sides; or lastly does it accumulate in the vessels and so convert them into bone? We may reply in answer to these queries that the earth substances employed in the generation of bone are without doubt introduced into the system in the same manner as the various other materials which are required for the development of the animal frame; that they are mixed with the mass of the circulating fluids; and that eventually by the influence which the arteries, in virtue of their vitality, exert on their contents those particles are separated from the blood which are necessary for the growth of the bone. I acknowledge that we are totally ignorant of the means by which aliment is changed into such a compound fluid as the blood, and how the constituent parts of the latter are separated in the various organs so as to accomplish their nutrition. I simply wish to state that there is nothing more wonderful or peculiar in the formation of a bone than of a nerve, a muscle, or a ligament.
Key Takeaways
- Early anatomists proposed various theories about how bones form and grow.
- Duhamel's theory suggested that bone layers are deposited from the periosteum, similar to tree rings.
- Haller's theory posited that bone formation occurs independently of the periosteum through internal vessels.
Practical Tips
- Understanding historical theories can provide context for modern medical practices and research.
- Observing changes in diet (like madder) on bone structure can offer insights into nutritional impacts on skeletal health.
Warnings & Risks
- Over-reliance on outdated theories without considering new evidence can lead to incorrect conclusions about biological processes.
- Ignoring the complexity of blood vessel interactions with bone formation may result in incomplete understanding of osteogenesis.
Modern Application
While this chapter focuses on historical theories, it underscores the importance of empirical observation and experimentation. Modern survivalists can benefit from these principles by applying them to dietary supplements or environmental factors that affect bone health during prolonged survival scenarios.
Frequently Asked Questions
Q: What was Duhamel's theory about bone formation?
Duhamel proposed that bones are formed through successive layers deposited from the periosteum, similar to how tree rings form. He supported this by observing changes in bone color when feeding animals madder.
Q: How did Haller's hypothesis differ from Duhamel's?
Haller believed that bones are formed independently of the periosteum through internal vessels, suggesting a more direct role for blood vessels in bone formation compared to Duhamel's theory.
Q: What does the chapter suggest about the origin and distribution of phosphate of lime in bones?
The chapter suggests that earth substances used in bone generation enter the body like other materials needed for development, mix with circulating fluids, and are separated by arteries to form bone.