When you look at a modern Siamese cats you think of length. Everything is long and slim from the head to to the tail.
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The head of the modern Siamese cat has a chiseled look, and should be wedge-shaped. The wedge starts from the tip of the nose and the line to the tips of the ears should be completely straight, forming a triangle, when seen from the front.
The head should be medium-sized and proportionate to the body, not too small. The neck should be slender and elegant. The profile is absolutely straight, there is no whisker break. The nose is long and straight, and continues to the forehead without a break.
The chin is well defined. Tip of the chin is in line with the tip of the nose in the same vertical plane. The chin should not recede, nor be massive. The muzzle if fine and wedge-shaped. Males are allowed some jowl.
The eyes of modern Siamese cats are captivating. They are brilliant sapphire blue - with variation from pale blue to deep blue. The color is caused by the partial albinism gene. Light reflects back from the retina revealing the breath-taking blue color (this is called the Tyndall's phenomenon). There should be very little, preferably no yellow pigment in the eyes.
The shape of the eyes is almond, and they are medium-sized. They should be an eye's width apart, no more. Also they should be neither protruding nor recessed (deep set). They are oblique, at a slant towards the nose, and in harmony with the lines of the wedge of the head and ears. They should be uncrossed, and should be expressive with a definitive presence, showing intelligence and emotion.
In the past Siamese cats often had crossed eyes, which was cased by an abnormal uncrossed wiring of the optic chiasm. This was caused by the same albino allele that causes the colored points in the Siamese's coat. These days this trait is mostly bred out. The same albino allele causes that the eyes of the Siamese lack tapetum lucidum. This means their eyes don't amplify dim light as it would in a normal cat, causing them to see better in dim light conditions. This may be a reason why the Siamese cats are somewhat less active at night.
Despite their light colored coat and blu eyes, the Siamese are not deaf. Deafness is caused by the same genes that cause pigment loss in skin cells. This is not the same gene that causes the color of the Siamese.
The ears of modern Siamese cats are very large and pointed. They are wide-based and should continue the wedge of the head - a perfect triangle should be formed if one draws a line from the tip of the cat's nose to the tip of the ear. The ears are positioned more on the side of the head than on the top.
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The body is of medium size, males are larger than females. The overall look is lean, angular, svelte. And elegant, definitely elegant and refined. The body is well muscled, yet delicate. And because of the musculature, when you lift the Siamese, the cat feels a lot heavier than it looks.
Both shoulders and hips continue the tubilar line of the body. The hips are never wider than the shoulder. And the abdomen should be tight.
The legs and paws of modern Siamese cats are of course long and slim. The hind legs are longer than the front legs, and they should be in good proportion to the body. The paws are ovail, dainty and small, as fits the overall elegance of this cat breed.
In the past a kinked tail was a breed characteristic of the Siamese cat, but this has been bred out. (You can still see this genetic trait in the street cats of Thailand). The tail should be slender and thin, whispy, and it should taper to a fine point.
The coat of modern Siamese cats fits its slim figure beautifully - it is short, glossy and silky, and lies close to skin. Before the Siamese cat became known people did not really know cats could have such silky coats. But since they met the Siamese, achieving a similar kind of silky coat became the goal of many breeders of other cat breeds as well.
The coat of the Siamese has no undercoat, and adheres closely to the body. Because of this the Siamese are sensitive to colds.
The coat darkens with age (from fawn color to a paler shade of the cat's point color). As the cooler parts of the cat are darker, if the cat gets fat, the coat also gets darker - the fat layer insulates the skin from the body heat. Interestingly enough this also causes the Siamese to show past fevers in its fur - the actively growing hairs may show "ticking" later, having experienced the higher temperature of the skin. You may see such ticking in the cat's mask, but it disappears when new hair replaces the old. Also in warmer climates the Siamese cats tend to have paler points and lighter coats.