In addition to chemical crystals, fibers, hairs, rocks, and minerals, a number of other types of specimen may benefit from observation through polarized light microscopy. The technique, for instance, readily reveals the striations present in many fish scales and samples of human muscle tissue, as well as the structural details of fossilized dinosaur bones. Utilization of polarized light microscopy can also reveal important information regarding harmful insects and parasites that afflict humans and other animals, such as the biting louse and the whipworm.

Canine Biting Louse (Trichodectes canis) - The canine biting louse has a dorsoventrally flattened body and a broad head, which together measure about 1.5 millimeters in length. The antennae of the tiny insect are quite prominent and each of its six legs is equipped with a powerful claw that enables the louse to hold tightly to its host, even when the canine is furiously trying to scratch or bite it away. As its classification as a biting louse implies, this species is also equipped with large, opposing mandibles that it utilizes to feed upon skin cells, hair fragments, and blood.

Ctenoid Fish Scale - Fish scales are typically divided into four main groups, one of which is comprised of ctenoid and cycloid scales. Both of these types of scales are similar in composition, consisting of a rigid surface layer primarily made of crystallized calcium-based salts and a deeper, fibrous layer predominantly composed of collagen. They differ, however, in shape. Cycloid scales feature a smooth posterior edge, but ctenoid scales display ctenii, bony, comb-like structures that decorate the outer margin of the scale.

Dinosaur Bone - The term dinosaur was originally coined in 1842 by British comparative anatomist Richard Owen from the Greek words for “terrible” and “lizard.” This association with reptiles was generated from the early study of fossilized bones and from the understanding that dinosaurs produced their young in the form of hard-shelled eggs. However, many more recent researchers have postulated that dinosaurs are actually ancient ancestors of birds, drastically changing the common perception of these intriguing animals.

Human Muscle - There are more than 600 muscles in the human body, which collectively comprise about 40 percent of one’s bodyweight. The tissues that constitute these muscles are typically classified, however, as one of three basic types: striated, smooth, or cardiac. Named for its banded appearance under the microscope, striated muscle comprises the bulk of muscle tissue in the human body. Sometimes alternatively known as skeletal muscle, this tissue type is usually attached to the body’s skeleton via fibrous tendons and is under voluntary control.

Human Whipworm (Trichuris trichiura) Eggs - Trichuris trichiura is the species of whipworm that is primarily found in humans. The parasites, which exhibit a tapered whip-like shape in their adult form, live in the host’s large intestine with their thin anterior ends implanted in the intestinal lining. They may remain there for several years, feeding upon tissue secretions and producing thousands of eggs daily that are excreted with bodily wastes. It is through the consumption of these eggs, which become infective after approximately three weeks, that new infections occur.

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