Poisonous Plant Diseases.—Milk sickness has been known in the Eastern States since the beginning of the 19th century. It was found in cattle. A prominent symptom being trembling, the disease was sometimes called the "trembles." In human cases the disease resulted in prolonged sickness, and caused many deaths. In some localities the cases were so numerous as to lead to the abandonment of settlements. It became evident that the human cases resulted from the use of butter or milk of milk sick cows, but for a long time the cause of the disease in animals was a matter of controversy. A plant with poisonous qualities was suspected but not until the present century was there proof that the disease in cattle was caused by white snakeroot, Eupa torium urticaefolium, and that human cases were caused by the poison excreted with the milk of diseased cows. In western Texas, New Mexico and Arizona, particularly in the valley of the Pecos river, there is a disease among cattle and men which resembles the eastern milk sickness so closely that it has been given the same name by physicians familiar with the eastern disease. Recently it has been shown that this disease is caused by a plant known as rayless goldenrod or jimmyweed, Aplopappus heterophyllus.
Poisonous Plants in Parts of the World Other Than Great Britain and North America.—Many of the poisonous plants of Great Britain and North America are found in other parts of the world, and, wherever found, have the same poisonous charac teristics. Many others, more or less localized in other regions, are of great interest because of their effects on men and live stock. The tropics of both hemispheres contain a great many poisonous plants, many of them being peculiarly deadly. Only a few of these
tropical plants have been examined, and it is an important field for further research.
The number of known poisonous plants is so large that a list would far exceed the limits of a general article on the subject, and a discussion of them would fill a large volume. A few of the more important and interesting plants will be briefly mentioned, and further information must be sought in special publications on the subject.
The effects of poisonous plants on live stock have been espe• cially studied in South Africa and Australia, for the local con ditions there, as in North America, frequently lead to very large losses.
Heavy losses of live stock have been caused in Australia by species of Swainsonia and Gastrolobium (family Leguminosae). Swainsonia galegifolia, commonly known as "indigo plant" or "darling pea," is especially destructive. The species of Gastro lobium, popularly called "poison bushes," are said by some to be the worst stock-poisoning plants in Australia. They affect cattle, sheep, camels and horses, and are particularly harmful in west ern Australia. Species of Homeria, of the iris family, known in South Africa as "tulp" or "Cape tulip," have produced many losses of cattle in South Africa and Australia. Many cases of poisoning of pigs by species of Melia, related to the chinaberry, have been reported in Australia, where these plants are called "white cedars." An Australian plant (Duboisia Hopwoodii), allied to tobacco, commonly called pituri, causes some losses of sheep. The giant nettle (Laportea gigas) of Australia is exceedingly virulent ; cattle are said to become furious when they come in contact with the leaves. (C. D. M.)