_Toxic Principle._ The Potato plant, like the other species of _Solanum_ mentioned above, contains _Solanine_, which occurs not only in the haulm, but in the flowers and fruits, and in the peel of the tubers. _Solanidine_ also occurs ready-formed in the young sprouts of potatoes to the extent of 1·5 per cent. (Allen). In the case of the soldiers poisoned in Berlin analysis demonstrated the presence of Solanine to the extent of 0·038 per cent. in boiled tubers and 0·024 per cent. in raw tubers, and on an average every man who fell ill had 0·3 gramme of the alkaloid, a sufficient quantity to produce toxic results. Esser (1910) states that in midsummer the haulm contains 0·0925 per cent. of Solanine but late in summer only 0·0374 per cent. In the tubers the alkaloid occurs in the inner layers of the peel to the extent of 0·0124 per cent., red or pink varieties containing rather more than yellow sorts. The same authority says that damp soils tend to a higher percentage of Solanine than dry soils[3], and that nitrogenous manuring as compared with potash tends to an increase of Solanine. In fresh spring shoots 1·5 per cent. of the alkaloid has been found, and the percentage is especially high in tubers which have been “greened” by long exposure to light. As already stated it is the greened tubers which appear to be the chief cause of accidents. Tubers with young shoots are richer in poisonous alkaloids than those which have not yet been sprouted; such tubers when fed raw to stock may on occasion induce poisoning, unless fed only in small quantities. Footnote 3: On the other hand, potatoes grown in a dry sandy soil are stated to contain more Solanine than those grown in other soils. Writing in 1887 Cornevin remarked that Solanine, though neither very active nor very abundant in Potatoes, nevertheless causes accidents, as it is cumulative, or, to be more exact, is eliminated slowly. _Symptoms._ In poisoning by potato _haulm_, Cornevin records constipation, loss of appetite, rise in temperature, accelerated circulation, normal respiration, salivation, tumefaction of eyelids, eyes watery, conjunctivæ injected, and hair erect. The skin is covered with scabs which exude matter, the skin being cracked. These scabs are found especially on the scrotum of male cattle and the udder of female cattle, but also in the caudal region and round the anus. An examination of the mouth shows places on the upper jaw which are devoid of mucus and are purulent at the centre, the mucus round the edges being swollen. The posterior members are similarly but not so badly affected. Movement of these members seems to cause the animal much pain. Defecation is frequent, the fæces being liquid and dark in colour. The animals are recumbent for a considerable time with the posterior members stretched out. In the worst cases there is pronounced emaciation.