Vulcanoid species make up nearly one third of the population of the Federation. Although "vulcanoid" has had different meanings, the definition in The Unabridged Federation Standard Dictionary is "a being similar in physical form and chemical makeup to the dominant humanoid lifeform on the planet Vulcan and its colonies, hence derivation of the term . . ." The Romulans are actually the descendants of Vulcan emigrants, so, for all intents and purposes, a description of Vulcan physiology will fit the Romulans as well.
For many years, it was believed that there was only one fairly homogenous race of Vulcans, so it was a great surprise when much darker Vulcans were first seen many years after Vulcan participated in the creation of the United Federation of Planets (UFP). Indeed, The Star Fleet Medical Reference Manual (ISBN 0-345-27473) states that there is only one race of Vulcans because Star Fleet Medical had no knowledge to the contrary at the time. Explanations have been vague and it is thought that these "dark Vulcans" are from a minority race that has historically been a private, possibly xenophobic cultural subgroup. Because of certain privacy clauses in the Vulcan UFP membership agreement, the details behind the "second race" of Vulcans is unknown. Rumor has it that there may be a third Vulcan race, somewhat analogous to the Asians on Earth but this has yet to be proven. It can be argued that the Romulans form a separate race of Vulcans as well or a subspecies, because of physiological changes which have occurred due to differing climatic influences and probable genetic engineering programs in centuries past.
The Vulcans of T'Khasi are generally a tall, thin people, falling in the upper average height range for humanoid/vulcanoid species. Adult males average between 6'-6'7" (1.8-2.0 m) in height, adult females 5'7"-6' (1.7-1.8 m). Weight is commensurate with height and build, although Vulcans weigh slightly more than expected due to tissue density. Muscle density and strong attachment to the skeletal structure make Vulcans much stronger for their size than most humanoids. Vulcans display a natural ability in many athletic events and martial arts. Their tall, thin body structure also aids in the dispersion of heat, the same as that of the similar body structure found in desert-dwelling peoples on many worlds, including Earth.
The biochemical makeup in Vulcans of T'Khasi and its colonies is very similar to that in many humanoid and especially vulcanoid species of known space. At the cell nucleus level can be found DNA and chromosomal structures similar to most humanoid/vulcanoid races, giving some support to the controversial theory that life throughout the Milky Way Galaxy had a common source untold billions of years ago. "Genetic seeding" also was apparently carried out by an ancient super-race of beings, often called The Preservers. Since vulcanoid species appear throughout the galaxy, it is obvious that some process led to this occurrence but an answer is unknown. T'Khasi is considered by many to be the evolutionary and genetic source for all known vulcanoids, because the Vulcans are genetically related to all other lifeforms on their planet, whereas the vulcanoids on many other worlds have turned out to have partially or completely different DNA to other lifeforms of those worlds.
The blood of most vulcanoids, including the T'Khasi Vulcans, is made up of hemoglobin based on copper. (Several primative vulcanoid species have been discovered with iron-based hemoglobin, just like that of most other humanoids, but we will not discuss that any further here.) This copper-based blood is most obvious from its green color, which also tints the tissues of Vulcans greenish, much like the iron-rich red blood of many other races tints their tissues a pinkish or reddish color. Having copper-based blood aids in the utilization of oxygen under the low atmospheric pressure and low oxygen conditions on T'Khasi. The Vulcan blood cells have a double-convex form, which in addition to helping to maximize oxygenation, also aids in cooling each blood cell, the blood stream, and ultimately the entire body. A lot of the waste heat conducted by blood cells is transferred into the lungs during respiration, thus making the exhaled breath of Vulcans fairly hot under most conditions, especially during exertion.
Sight -- as in most humanoid/vulcanoid species, Vulcans have a forward-facing, stereoscopic pair of eyes. Each eye is protected by a clear inner eyelid or nictating membrane (tvi-wein t'bezhun) that helps filter out harmful radiation, heat and dust. Vulcan vision is less acute in bright light, while their night vision is more acute. This is thought to be due to the fact that the Vulcans descended from nocturnal predatory "cat-apes". As in most very hot and arid climates, most life on Vulcan was and is nocturnal, sheltering from the blistering heat during the day and only coming out during cooler temperatures at night. Because of their eyes, Vulcan living accommodations or vessels are much more dimly lit than those of most other species. Most Vulcans find the lighting of standard Star Fleet vessels on the bright side, although they find the lighting of Romulan or Klingon vessels comfortable. It has recently been discovered that many Vulcans serving on mixed Star Fleet vessels wear a type of tinted, polarizing contact lens to enable them to work without unnecessary and unhealthy eye strain.
Hearing -- as in most humanoid/vulcanoid species, Vulcans have a pair of ears on each side of their heads. The ears of most vulcanoids are very distinctive in that the top of the external ear structure tapers into a clearly defined point. This is the case with the T'Khasi Vulcans and their descendants. There appears to be a clear sexual dimorphism in ear shape, with males tending to have bigger ears with more prominent points. It has long been suspected that some Vulcans cosmetically alter the shape and angle of their ear tips to conform to an aesthetic standard. This may be supported by the fact that certain societal outcasts, Vulcans who chose to live a non-technical, traditional life, and members of certain monastic groups seem to have much longer, and often curved, ear tips. The hearing of the Vulcans, and indeed that of most vulcanoids, is very acute under most conditions. While the Vulcan low frequency hearing range is nearly identical to humans, their high frequency hearing range is significantly higher. This is to be expected in beings descended from predatory, nocturnal creatures living in a thin atmosphere.
Smell -- the size and shape of the nose of Vulcans conforms to the normal range of most humanoid/vulcanoid species. Because of their evolution in a hot, arid environment, though, the nose of the Vulcans has become highly adapted to filtering dust and sand from the air during inhalation, and minimizing moisture loss during exhalation. Because the sinus spaces of the Vulcans contain moisture-reclaiming cells in place of what would be a large number of olfactory cells in other beings, the sense of smell of Vulcans is not nearly as acute as that of most other humanoid species.
Taste -- the size and shape of the tongue of Vulcans conforms to the normal range of most humanoid/vulcanoid species. Unfortunately, due to the fact that taste is related to the sense of smell, Vulcans have a well-known lack of taste sensation. Vulcans are especially weak in tasting sweet things, although their sense of taste for salty and bitter things is relatively good. In order to enjoy the taste of things, Vulcans have historically tended to highly spice or season their foods. Some traditional Vulcan dishes are nearly impossible to eat by other humanoids.
Touch -- as is the case with most vulcanoid species, the Vulcans have a very acute sense of touch in all its forms, especially heat, pressure and texture. Vulcans are tactile beings by nature but must, by necessity, limit their contact with living beings because of their innate telepathic abilities. One of the strongest taboos in Vulcan culture is making uninvited physical contact. Even husbands and wives often only touch each other with one or two fingers at most in day-to-day situations. Contact such as hand-holding, hugging or kissing is unknown in civilized Vulcan behavior. It is only accepted and considered normal for infants and toddlers to make much physical contact with others. Unfortunately, it is the normal behavior of most humanoids to grasp hands, embrace, or make other such physical contact during greeting and conversation. This behavior is very uncomfortable and even distasteful to Vulcans, but they have learned to bear it as the price of living and working with non-Vulcans.
Skin -- the epidermis of Vulcans, unlike that of many other humanoids, is a twin-featured moisture-proof barrier to prevent dehydration. Vulcans have almost no sweat glands as an evolutionary development to conserve moisture in an extremely hot, arid climate. Most excess heat is drawn away by the blood to be exhaled or stored and radiated from the skin when external temperatures are lower. This is why Vulcans have a very warm breath and their skin is almost hot to the touch under most conditions. Another difference in the skin of Vulcans is the fact that, even though the skin does not give off much moisture, it can directly absorb moisture from surrounding air, if there is any. In prehistoric times, Vulcans would stand in rare fog or rainfalls nude to maximize absorption of precious water that the body then stored. This technique is taught to the present day as a survival tool.
Brain -- externally, it is difficult to tell the Vulcan brain from that of most sentient humanoid/vulcanoid species. Of course, if a human and Vulcan brain were set side by side, it would be possible even for a layman to tell which was which simply by color -- the human brain is greyish with a pink tinge, whereas the Vulcan brain is greyish with a green tinge. A normal Vulcan brain is about 1600 cc in size, practically identical to that of humans. The olfactory center of the Vulcan brain is smaller due to function (see the "Nose" section above), while the Vulcan mid-brain is somewhat larger and more convoluted than that of a human, explaining the telepathic powers all Vulcans possess to one degree or another. Unlike the early medical knowledge of many humanoid/vulcanoid species, which centered the mind in various parts of the anatomy, as far back as their history is recorded, Vulcans knew the brain was the site of thoughts, memories, knowledge and emotions.
Heart -- the Vulcan heart is located approximately where one would expect to find the liver in most humanoids. It is believed that the Vulcan heart was displaced to allow additional space for the lungs which, by necessity, are somewhat larger in order to extract sufficient oxygen from a thin atmosphere. In order to protect the heart region, cartilaginous ribs extend lower on the torso of a Vulcan. Another consequence of the position of the heart and lower ribs is that the fetus is carried quite low in Vulcan women, often causing discomfort for most of the pregnancy. The adult Vulcan heart rate is approximately 240 beats per minute and normal blood pressure is 80/40, both far from the norm of most humanoids. The Vulcan heart is larger than humanoid/vulcanoid average for body size due to the increased workload of the heart in not only circulating blood to feed the tissues and remove wastes, but also to aid in the cooling of the body.
Liver -- the Vulcan liver is much smaller than that of most humanoids because many of the functions it has in other humanoids is done elsewhere in the Vulcan body. For example, the Vulcan kidneys not only filter fluids, they filter out and store certain substances. Other parts of the digestive and circulatory systems also have additional functions.
Kidneys & Bladder -- in some ways the kidneys of the Vulcan are more important than any other organ, since they manage the body's water retention system. In pre-technical times, kidney disease was the number one medical condition that caused a premature death, whereas cancers or heart disease were the cause in most other humanoids. The Vulcan urinary system passes slightly less than half of all water taken into the body, while the rest is recycled. This is an adaptation to life on a very dry, arid planet where water is rarely found in its natural state. The urine of Vulcans is relatively thick and viscous, actually more like an oil than a watery liquid. The Vulcan bladder can hold urine for a number of days, unlike the bladders of most humanoids which have to be drained at least once a day and usually more often. The lining of the bladder also plays a small part in retrieving some water before the urine is finally eliminated.
Stomach & Digestion -- as with all known true humanoid/vulcanoid beings, Vulcan digestion begins in the mouth with the chewing of food and its mixture with saliva. As part of their evolutionary development to conserve moisture, Vulcans do not salivate from emotional or external sensual cues. Food has to actually be in the mouth being chewed before saliva will be released. After swallowing, the food bolus travels down the esophagus to the stomach with peristaltic contractions. The esophagus is separated from the stomach by the esophageal valve ("cardiac sphincter" in humans). The Vulcan "stomach" is actually two joined chambers -- the first section is a spherical muscular object and the second section is a flattened oval object. The two sections are separated by the first pyloric valve. In the first stomach, the undigested food is mixed with acids and enzymes, then subjected to vigorous muscular contraction until it is broken down into a mash. After formation of this mash, the first pyloric valve opens and the contents enter the second stomach. The first valve closes, as well as a second pyloric valve at the posterior end, if not already closed. The second stomach is where the mash from the first stomach is subjected to more intense acids, bile and enzymes, quickly reducing the contents to their basic components. After digestion is complete, the second pyloric valve opens and the soupy mixture enters the intestine where absorption of nutrients and water takes place.
Because civilized Vulcans have been vegetarians for many centuries, most Vulcans are unable to digest meat products of any kind should a survival situation require it. Most Vulcan first aid or survival kits contain packets of oral enzyme supplements for use in such emergencies. Replicated meat substitutes, based on plant proteins, do not require such supplements.
Intestine & Excretion -- the intestine of the Vulcans plays the same role as it does in all lifeforms with one, absorbing nutrients and water, and packaging wastes for excretion. The intestine of Vulcans is very simple compared to those of most humanoid species. Instead of a complicated system of duodenum, jujunum, ileum, and large intestine, the Vulcans only have a continuous coil of intestine that is a blend of features from the small and large intestines of other humanoids. The Vulcans do not possess an appendix. As with all Vulcan body systems, the intestine of the Vulcan body is very efficient, and the feces that is eliminated is a fairly dry, compact mass. Diarrhea, although very rare, will kill a Vulcan much quicker than most humanoids, unless copious amounts of water are ingested immediately to replace what is lost. According to the Vulcans, constipation and hemorrhoids are unknown to them, although Federation medical expects are dubious of this claim, despite never encountering either condition in a Vulcan to date!
Reproductive Systems -- as with the vast majority of known humanoid/vulcanoid beings, the Vulcans are differentiated into male and female genders. In response to extreme environmental conditions, where mortality is high, all native T'Khasi animal life, including the Vulcans themselves, can breed at any time during the year. The Vulcan female is always fertile. The Vulcan male can mate at any time, but must mate every 7 years during pon farr or he will die. Vulcans will not readily discuss this subject with non-Vulcans, but Federation doctors and biologists have noted this 7-year cycle in all Vulcan animal life to one extent or another. It is now believed that all Vulcan life was synchronized in this 7-year cycle at some point in the very distant past. Astronomers have noted a 7-year cycle of solar activity in the Vulcan star system and it is believed that animal life on T'Khasi evolved to breed without fail during this time of especially low solar activity when radiation levels of all kinds were at their lowest.
The Vulcan male reproductive organs parallel those of most other known humanoid/vulcanoid beings. The Vulcan penis is an erectile structure without external sheath or foreskin, therefore Vulcans have no need for circumcision. As part of the evolutionary process of T'Khasi life, the male organ is almost fully retracted into the body when not in use as a protective measure. Vulcans also have two testes in a scrotal structure that is close to the body, not pendulous, and a prostatic body that produces and stores seminal fluid. Once ejaculated, the sperm of Vulcans is viable for a maximum of about 30 hours before losing mobility. It is believed that Vulcan males remain fertile during their entire adult life.
The Vulcan female reproductive organs also closely parallel those of other known humanoid/vulcanoid beings. They are comprised of a vagina, uterus and ovaries. There are no lengthy uterine or Fallopian tubes in Vulcan women; the ovaries are directly connected to the uterine body by short ducts. As part of the evolutionary process to conserve body water, Vulcan women do not menstruate. Ovulation occurs each month from alternate ovaries. The ovum enters the uterus usually in less than a day, where it remains awaiting fertilization. If no fertilization takes place within 10-14 days, the ovum deteriorates and its substance is absorbed into the uterine lining. Should fertilization occur, the blastocyst will implant itself in the uterine wall and hormones will activate formation of a placenta. Growth and development of a fetus will occur within the uterus with delivery being made through the vagina. The need for Caesarian types of deliveries, although rare, is not unknown to Vulcans. Twinning is very rare in Vulcans, probably as a consequence of evolving on a planet where scarce resources would favor only survival of one infant at a time. Fraternal twins are exceedingly rare, whereas indentical twins are the norm. Multiple births beyond three are unheard of. The idea of giving birth to multiple children is considered repugnant to most Vulcans and may be innate. It is unknown how long Vulcan females remain fertile, although it is believed that it lasts well into maturity. Vulcan women on T'Khasi rarely have more than two children in a lifetime, unless they need to replace a child that died, but Vulcans on colony worlds are known to have as many as five children.
