Section III.
THE PROPERTIES OF FAT.
The colour of fat, which is yellowish white, varies in different life stages, being whiter and more transparent with youth. The yellow hue is due to a soluble coloring principle that can be washed out by water. Human fat removed from its vesicles resembles purified oils; after purification, it has no odor, mild taste, and floats above water at body temperature. It burns rapidly but becomes rancid when exposed to air and light, emitting volatile acids with strong odors. By reacting with alkaline substances, animal fats yield margaric and oleic acids plus glycerin. Fat is one of the few animal substances without nitrogen; it consists solely of carbon, hydrogen, and oxygen.
Fat was once considered an immediate principle of organization until M. Chevreul demonstrated that it comprises two substances: a fluid called elaine and a solid named stearine. Elaine remains liquid at zero degrees Celsius but solidifies below this temperature. It is colorless, odorless, and tastes mild. Stearine appears white and shiny; when heated, it liquefies readily. The degree of fat's combustibility depends on the proportion of these two substances. They can be separated by treating fat in boiling alcohol; cooling precipitates most stearine as small white crystals while elaine remains dissolved with alcohol.
II' Section IV.
FUNCTIONS OF THE ADIPOSE TISSUE.
The functions of adipose tissue are not well understood despite extensive discussion. Its primary role is to secrete the fat it contains, a process that occurs through arterial perspiration rather than glandular secretion or follicles. The separation of fat from blood remains unclear but likely involves the vessels supplying adipose vesicles. Observations suggest that fat forms in the blood, possibly derived from chyle.
Adipose tissue serves multiple roles when considered as an entire organ. Mechanically, it moderates pressure effects and supports organs like the eye's globe. It fills voids with cellular tissue to maintain rounded body shapes and acts as a poor conductor of heat, potentially helping retain internal body temperature. Some believe fat makes surrounding parts supple or protects skin through transudation; however, this is unproven.
The most general use of adipose tissue is as a nutritional reservoir, where stored fats are absorbed when digestion-based nutrition is suspended. This is evident in hibernating animals that lose significant weight after prolonged dormancy. A notable example includes a hog buried for 160 days without food or water, surviving by absorbing body fluids into its circulatory system.
It has been suggested that nutritious matter passes through various states before assimilation with the body, including fat as one condition. However, this is not always accurate since nutrition can occur perfectly in fetuses and individuals with minimal fat like athletes.
The chapter continues to discuss serous membranes but is omitted here for brevity.
Key Takeaways
- Fat serves as a nutritional reservoir when food is scarce.
- The composition and combustibility of fat are influenced by its molecular structure.
- Serous membranes play roles in protecting organs and facilitating movement.
Practical Tips
- Store fats properly to prevent rancidity, ensuring they remain usable for energy.
- Recognize natural sources rich in fats as potential emergency food supplies.
- Understand the role of adipose tissue in maintaining body temperature during cold conditions.
Warnings & Risks
- Improper storage can cause fat to become rancid and unusable.
- Over-reliance on stored fat without proper nutrition may lead to health issues.
- Serous membranes, while protective, can develop adhesions due to inflammation or injury.
Modern Application
While the chapter's focus is historical anatomy, understanding fat properties and functions remains crucial for modern survival scenarios. Knowledge of how fats serve as nutritional reserves during starvation periods and their composition aids in identifying natural food sources. However, advancements in nutrition science have refined our understanding of optimal dietary practices.
Frequently Asked Questions
Q: What are the primary roles of adipose tissue?
Adipose tissue primarily serves to secrete fat and acts as a nutritional reserve when digestion-based nutrition is suspended. It also moderates pressure effects, supports organs, fills voids in body shapes, and potentially helps retain internal body temperature.
Q: How does the composition of animal fats differ from other substances?
Animal fat is unique because it contains no nitrogen; instead, it consists solely of carbon, hydrogen, and oxygen. This makes it one of the few animal substances without azote (nitrogen).
Q: What happens to stored fats during hibernation?
During hibernation, animals are very fat when entering dormancy but lose significant weight by spring due to absorption of stored fats. This illustrates how adipose tissue acts as a nutritional reservoir.