The human body is a somewhat complex structure. Regarding complexity, the human body has an immune system that always protects it from germs that may cause any harm. The human immune system always strives to protect us from any harm that may lead to the deterioration of one’s health. As for the immune system, it produces antibodies that act as weapons that in turn fight the illegal materials that appear within the body. The antibodies devour the illegal materials within the body, whereas others notify organisms such as leukocytes that there is a presence of illegal materials within the body.
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In man the blood constitutes about 5 per cent, of the total body weight, in rabbits about 5 per cent., in dogs 7 or 8 per cent., in rats 61/2 per cent., in guinea-pigs 4 per cent., and in mice 6 per cent. Young animals tend to have relatively rather more blood than old individuals of the same species. Under most circumstances the volume is kept almost constant, and it is difficult to produce any material, and especially any lasting, alteration in the volume by experimental procedures.
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The sleep is structured in cycles. The number and length of the cycles vary by age and individuals but on average for an adult the cycle lasts 90 minutes and about 4-6 cycles occur per night. Each cycle is divided into two parts: the non REM (non-rapid eye movement) and the REM (rapid eye movement) sleep. Dr. Michel Jouvet discovered the phase called "REM sleep." In the late 1950s, he made experiments on cats and noted a phase of rapid cortical activity identical to the waking phase. In 1962, Jouvet presented the necessary arguments to validate his theory on sleep, theory that states two dependent states of different structures and mechanisms.
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During normal life destruction and regeneration of red cells is constantly going on. Why this should be so we do not know ; it is convenient to say that red corpuscles ultimately wear out, and to attribute their destruction to a process of natural senescence. How much blood is thus changed every day is unknown, nor have we any idea of the natural length of life of a red cell. The constant activity of the marrow and the steady formation of bile pigment show, however, that there is a normal destruction.
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