reverse, however, has been proved by several observers. Fourcroy relates an experiment in which there was an EVOLUTION or CALORIC AND OP CARBONIC ACID. 39 incrc&iic of heat to the amount of 11°. The late Dr. Gonlon confirmed this ; the increase in one of his experiments being 6°. Dr. Davy, and others, however, state that the disengagement of caloric is very slight. Dr. Philip has proved, by direct experiment, that galvanism diminishes the temperature of arterial blood 3° or 4°; it also renders it dark-coloured. It is remarkable, that the galvanic power has no effect upon the warmth of venous blood. <Callout type="tip" title="Tip">Understanding these factors can help in assessing a patient's condition during triage.</Callout> Whilst the coagulation is proceeding, a considerable quantity of carbonic acid gas is extricated. This was noticed by Sir E. Home, who founded a curious hypothesis on it, with respect to the organization of the fibrin. Dr. Scudamore has also performed some experiments which tend to prove the disengagement of carbonic acid. The blood, after it is taken from its vessels, remains fluid for a short time; the duration of which is influenced by many causes. Subsequently, it begins to assume the solid form, a thin film being first perceived upon the surface, and afterwards, as the change proceeds, the whole mass is converted into a soft jelly. This soon gives way and divides into two parts; one consisting of a firm cake, and the other of fluid. The first is called the crasamentum, the cruor, or the clot; and the second, which surrounds it, is named the serum. <Callout type="important" title="Important">The formation of these components can help in diagnosing conditions such as inflammation.</Callout> The concretion usually commences in about 3-1/2 minutes after the blood has been abstracted from the body, and the whole is jellied in about 7 minutes, although often not until 16 or 20 minutes; and frequently a much longer period is required, the blood being but partially coagulated in 24 hours. At the end of 10 or 12 minutes the serum begins to separate, so that on cutting into the clot at that time, the incisions are immediately filled up with fluid. It often happens, that after the apparently complete separation of the crasamentum from the serum has taken place, the former continues to contract even during several days, thus pressing out and increasing the quantity of the latter.* Venous blood coagulates more speedily than arterial, and a small quantity sooner than a large one. The period of coagulation is greatly influenced by the state of the vascular system. The ingenious Hewson contended that concretion occurs speedily in proportion to the depression of the vital actions; an opposite opinion was entertained by Mr. Hiry, of Leeds. We are indebted to Mr. Thackrah, of the latter place, for determining the question by the most conclusive investigations. These consisted in receiving blood from the same animal into different cups in a full uninterrupted flow, and noting the time at which coagulation commenced in each cup: it was observed that coagulation always began first in the blood which was last removed, and last in that which was first removed. <Callout type="risk" title="Risk">Incorrectly assessing the state of coagulation can lead to misdiagnosis.</Callout> There is a point of great practical importance connected with the process of coagulation. I include to the formation of the sizy or huffy coat. This consists of a tough, elastic, yellowish substance, which is placed at the upper part of the crasamentum. Its thickness varies from the 1/40 to 1/20; or 1/30 of an inch. It is frequently concave or cupped upon its surface. The buffy coat is usually observed in blood which has been abstracted during inflammation, although it is occasionally seen in other states of the system. It is also in most cases found in venous blood. The late Dr. Gordon was in the habit of exhibiting a specimen of it in arterial blood. I have also had an opportunity, through the kindness of my friend Dr. Twedde, physician of the Fever Hospital, of seeing the sizy coat imperfectly formed in some blood which had been taken from the temporal artery of a man labouring under fever. The cause of the formation of this peculiar crust is not well known. Hewson thought, but erroneously, that the blood was attenuated in inflammation, and that the red particles thus more readily subsided into the lower part of the cror, leaving the lymph or fibrin at the upper part. But, as the quantity of fibrin is actually increased during inflammatory action, some other cause must be sought for its formation. It is known that blood, which is taken from a person who suffers from acute inflammation, remains for a long time fluid than it does under ordinary circumstances. Now, this being the case, the red particles, which are brawnier than the lymph, have a longer time to subside to the under part of the crasamentum, and, consequently, to leave the fibrin on the superior surface, where it causes the crust we have been describing. The sizy coat occasionally presents in diseases of debility, especially in hectic fever. It is probable, in these instances, that the blood is attenuated on account of the accumulation of phlegm, and that the explanation of Hewson is here correct. The cause of the coagulation of the blood is but imperfectly known, notwithstanding the numerous attempts which have been made to discover it. It is needless to enter into the detail of the many experiments which have been instituted, as most of them merely prove what are not the causes of coagulation. The exposure to cold and to atmospheric air, and the loss of motion, each, in turn, has been supposed to produce the concretion of this fluid. None of these causes is in the least sufficient to effect the process, although they may more or less assist in promoting it.
Key Takeaways
- The coagulation of blood is influenced by various factors such as temperature and the state of the vascular system.
- The formation of the crasamentum (clot) and serum can indicate underlying conditions like inflammation.
- The size and presence of the buffy coat can provide diagnostic information.
Practical Tips
- Monitor the coagulation process carefully to avoid misdiagnosis, especially in cases of acute inflammation.
- Understand that venous blood coagulates more quickly than arterial blood, which is useful for triage purposes.
- Recognize the importance of the fibrin component in diagnosing conditions such as inflammation.
Warnings & Risks
- Incorrectly assessing the state of coagulation can lead to misdiagnosis and improper treatment.
- The presence of the buffy coat may indicate a serious condition, but its absence does not necessarily mean everything is fine.
- Factors like temperature and vascular system state significantly influence blood coagulation.
Modern Application
While the specific experiments and theories described in this chapter are historical, the principles of understanding blood coagulation remain relevant for modern survival preparedness. Knowledge of how to assess blood coagulation can help in triage situations, especially when dealing with injuries or infections. However, modern medical techniques have improved upon these methods, offering more precise tools and faster results.
Frequently Asked Questions
Q: What is the significance of the buffy coat in diagnosing conditions?
The buffy coat, a yellowish substance that forms on top of coagulated blood, can indicate inflammation or other serious conditions. Its presence or absence should be noted as it provides diagnostic information.
Q: How does temperature affect blood coagulation?
Temperature has a significant impact on the coagulation process. Cold temperatures slow down coagulation, while warmer temperatures speed it up. Understanding this can help in assessing and managing patients under different environmental conditions.
Q: What are the main components of blood as described in this chapter?
The main components of blood include serum (the fluid part), fibrin (a tough, elastic substance that forms a clot), and red particles. These components can provide insights into the patient's condition during triage.