by: Giovanni J.R.C.

It is quite staggering how many people still hold to the archaic idea that some parts of the body are rudimentary and are therefore useless. Although there are hundreds of documentations that state otherwise, a large part of the population still claim that this notion is true. Because of such stubborn sentiments, the idea of vestigial organs still continues to survive until now even though it has been mostly disproved.

Such an erroneous concept can be observed as many people in earlier centuries regarded the thymus as one of the many useless organs in the human anatomy. Located around the upper chest area within the sternum, many early scientists believed that this organ was vestigial because it was not connected to anything else within the body aside from it’s main articulation. Furthermore, due to it’s changing in form from a large, healthy looking gland during childhood into a shriveled, disappearing mass of tissue as one matures in age, many even ventured to conclude that this organ was a hazard to people’s health (JAMA, #2). This process is now understood and is named “involution” and is regarded as a normal progression of this organ as it regulates the early development of the body’s immune system.

Early in the history of science however many other scientists speculated on the importance of the thymus. Galen, a Greek physician from the 2nd Century A.D., was perhaps the first to venture a published guess. According to him, this irregularly shaped mass found above the heart was the “seat of courage” (JAMA, #1). Some ancient philosophers even argued that such an organ was the “abode of the soul.” Even the name Thymus itself is believed to be named after the Greek plant called thyme. Incidentally, this word was also synonymous to the notion of spirit (JAMA, #1). Although quite prosaic, these people had the right idea regarding the true importance of this small mass of cells.

During the 1950’s, however, the purpose of the thymus was finally revealed. Although not precisely decided what it’s exact function was, the thymus was unequivocally identified as a lymphoid organ. This was achieved by observing the correlation between the decreased resistance due to disease and an individuals reaction to vaccines. This was because, upon the damage of the thymus due to injury, there was a decrease in the immune response (JAMA, #3). To further elaborate on this idea, various experiments were conducted to understand the true function of the thymus. One such experiment was conducted by removing the thymus (thymectomy) of newborn mice. As a result of such an operation, these animals were no longer able to reject skin grafts from other mice thus leading to infection and disease. Antibiotic responses were also greatly impaired in these animals thus making them susceptible to various injuries and certain forms of cancers. As a secondary response, perhaps to their inability to mount any kind of bodily defense, these same mice also underwent a type of “wasting disease” that eventually led to the deaths of many (#3). However, the transplantations of thymus cells somehow restored some semblance of immunities to all the mice that received this secondary surgery. This implies that the thymus had something to do with the development of the immune system. To determine whether or not this organ’s functions were quite limited during childhood development, the same experiment was also conducted on mature, and fully developed mice. In contrast to the first experiment, the thymectomy these animals underwent did not bare any changes on their health thus exposing the fact that the thymus’ influence on the immune system decreases as the organism ages.

What does the thymus do exactly? During the early stages of fetal life and the neonatal period, the reticular structure of the thymus entraps immature stem cells arising from the bone marrow and circulating in the blood stream (Miller, #1233). These cells are then processed by the organ making them capable of maturing into lymphocytes. These lymphocytes are important for the development of cell-mediated immunity. After sensitization by the thymus, the lymphocytes then re-enter the blood stream and are moved to emergent lymphoid tissue. Here, these tissues stimulate cells that eventually develop into thymus-dependent or T-lymphocytes.

Knowing this, it is then obvious that the removal or the failure of the thymus leads to the none-development of the cell-mediated portion of immunity which is concerned with delayed types of responses (Miller, #628). Some examples of this type of immunity is as follows: rejection of transplanted organs, defense against slowly developing infections, delayed hyper-sensitivity reactions, rejection of self-altering cells, some allergic reactions, and many other.

Around 1960, a group of researchers from the University of Texas discovered a type of hormone believed to be from the thymus (Miller, #1233). The discovery of this hormone, now called Thymosin, stimulated the imagination of many scientists thus prompting them to come up with various ways to use this hormone. One such example is the possible development of an anti-thymosin which may help some patients from suffering organ rejections. Another possibility is the use of this hormone to restore immune functions to immune-deficient patients.

In conclusion, due to early misconceptions, biases and prejudices, many organs that have important functions in the human anatomy were dismissed as useless remnants of once important structures. The thymus was once a part of this category of constructs called rudimentary or vestigial organs (perhaps due to its lack of articulation and absence of ducts thus making it seem useless). Due to the increased popularity of the early evolution theory, many early scientists found a way to use these seemingly useless organs as one of the many assumed evidences for their argument. This was, however, found fraudulent and is now mostly discredited. Furthermore, before the advent of the evolutionists, many researchers and philosophers actually thought that the thymus was vastly important. And in actuality they were somewhat right by thinking that this organ has a significant function in the human anatomy. It was however ironic that this organ, that is so essential to life and continued health, was once believed to be hazardous to the body just fifty years ago.

Internet, (1999). JAMA: The Thymus and Immunologic Reconstruction. www.ama.assn.org/special/hiv/newsline/briefing/thymus.htm.

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