This section is from the book "A Guide To The Poisonous Plants And Weed Seeds Of Canada And The Northern United States", by Robert Boyd Thomson, H. B. Sifton. Also available from Amazon: A guide to the poisonous plants and weed seeds of Canada and the northern United States.
The drug Ergot is believed to have been used by the ancient Jews before the dispersal of their nation. It was certainly used in medicine long before the details of its growth were discovered. While it has for years been known to be a fungous disease, there are still people who are ignorant of the fact and believe that the "ergots"* that grow on their grains or grasses are merely degenerate kernels. Its history as a poison is also very old. Epidemics of ergotism were recorded in the time of Julius Caesar, and since then the plague has recurred again and again, usually following rainy seasons. In America it has caused great losses. It is most dangerous in hay, but gives trouble also in ground feeds.
Repeated small doses such as an animal may obtain by eating infected hay or grain have a cumulative effect, causing chronic ergotism. This disease is due to the action of the drug on the nervous system, and may become evident in either of two forms, depending on whether the sympathetic or central nervous system of the animal proves more susceptible.
In the gangrenous type, which is the more common, the sympathetic nerves are affected. The arterioles, which connect the arteries and capillaries of the body, are controlled by sympathetic nerves. Ergot, by stimulating these, causes a contraction of the arteriole walls and produces two secondary effects. Since the blood can with difficulty be forced through into the capillaries there is much increased blood pressure in the heart and arteries, and more important than this, the tissues, especially those of the extremities, cannot obtain a sufficient supply of blood. This shows itself first in coldness, paleness and loss of feeling in the extremities. Later the tissues die, producing the condition known as gangrene. The ears, hoofs and tail often slough off, and gangrenous sores may form on other parts of the body. Gangrene may set in very quickly if the quantity of ergot eaten is sufficient. An extreme case has been recorded of a horse that was given a feed of badly ergotized hay. At the end of the first day the left hind leg was cold, stiff and moist with sweat. In two days gangrene had commenced, and in three the animal died - the skin and some of the muscles of the affected leg having already sloughed off.