A curious feature of Parkinson`s disease is the opposite of propulsion—retropulsion, or falling backward. Under these circumstances, of course, the patient could not run to catch up with his center of gravity. On the contrary, he did nothing, which was the most curious aspect of the symptom. Normal individuals, toppling backward for any reason, instinctively try to save themselves by thrusting their arms back of them. This instinctive "automatic" movement was entirely absent in patients with the shaking disease.
Despite the studies of certain notable clinicians and scientists down through the ages, however, no major contribution to the literature of the disease or the plight of the sufferer was made until a famous English scientist, Doctor James Parkinson, one day early in the nineteenth century, noticed that he was beginning to develop a rhythmic and unmistakable tremor in his right hand, the commonest site for the earliest forebodings of the "shaking disease.*"
An ordinary mortal in those days, watching himself slipping into this quagmire, coming down with as hopeless a condition as the shaking disease, might have been justified in becoming as paralyzed by fright as by the disorder, as tremulous from despair as from sickening nerves. Doctor Parkinson, however, was no ordinary mortal. Furthermore, he was by inclination and training a research scientist. He thereupon made a study of the "shaking disease," as manifested in himself as well as in others, and it became a dominant in¬terest during the latter part of his life. The fruit of this monumental study is contained in his classic "An Essay on the Shaking Palsy."
This contains a description of the disease which, though supplemented in detail since, has not in the main been improved upon to this day.
Actually, Doctor Parkinson's principal contribution was his meticulously detailed classification of the "shaking disease" and his dignifying it conclusively and unequivocally not as a mysterious jumble of nerve symptoms, but as a specific disease that should be treated and studied as such.
The so-called shaking disease, he asserted, henceforth should be known as "shaking palsy," to describe its symptoms and effects more literally. The term "palsy," signifying paralysis, denoted the symptom which, besides tremor, was its most disabling feature. Although present in widely varying degrees in the early stages of the disease the palsy usually progressed, the doctor wrote, to a point where the patient existed as little else but a framework of flesh, whose only remaining power of motion, ironically enough, was a constant shuddering which he could not stop.
Scientists since Doctor Parkinson's day have learned that Parkinson's Disease exists in a number of different forms, which depend upon a variety of causes. No attempt will be made here to describe each of these forms in minute detail, lest the general reader be more confused than informed thereby. Instead, we shall consider, in the following paragraphs, a composite, over-all picture of the disease, in the Doctor Parkinson, in his essay, describes only a single type of shaking palsy, whereas subsequent investigators have classified several kinds, each with a different cause. Inasmuch as the major symptoms of all types are similar, the term "Parkinson's Disease" is usually employed as an all-inclusive designation..
* Actually, the term "paralysis" is a misnomer. What appears to be a paralysis is in reality a stiffening of the muscles.