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In the blood of 15 patients with yusho or "polychlorinated biphenyl poisoning" that occurred in 1979 in Taiwan, was found polychlorinated dibenzofurans (14 of 15) and polychlorinated quaterphenyls (15 of 15), as well as polychlorinated biphenyls (15 of 15). The mean concentration ratio of these substances was approximately 1 : 160 : 500. Based on the following evidence, we propose that polychlorinated quaterphenyls were major pathogenic substances in the development of yusho: (1) Clinical manifestations and course of yusho patients are disproportionately severe and persistent for the observed blood levels of polychlorinated biphenyls, while patients who were occupationally exposed to pure polychlorinated biphenyls take characteristically mild and benign clinical course despite polychlorinated biphenyl levels often much higher than those noted in yusho patients; (2) Polychlorinated debenzofurans show a marked tendency to accumulate in the liver, which might explain frequent presence of jaundice and other abdominal symptoms in yusho, which are, again, not observed in those with occupational polychlorinated biphenyl poisoning; (3) Toxicity of polychlorinated dibenzofurans is a hundred to ten thousand times greater than that of polychlorinated biphenyls and polychlorinated quaterphenyls in animal experiments.

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Two toxic proteins were purified from the seeds of Abrus precatorius by DEAE‐A 50 and Sepharose 4B chromatography. One of them does not bind on the Sepharose 4B column (Abrin‐b) and the other (Abrin‐a) is eluted with 0.2 M galactose. The amino acid compositions and tryptic maps of these two proteins were similar, but not identical. The molecular weights estimated by SDS‐gel electrophoresis were 67,000 for abrin‐b as compared with 65,000 for abrin‐a. In the presence of mercaptoethanol, both abrin‐a and abrin‐b gave rise to two bands.The lethal doses of abrin‐a and abrin‐b for mice recorded within 48 h were 10 and 25μg per kg of body weight respectively. Abrin‐a at 0.8 μg per ml concentration level agglutinated human 0‐type erythrocytes, whereas abrin‐b showed no such activity. Abrin‐a at 5 μg per ml concentration level agglutinated both the Sarcoma 180 cells and Ehrlich ascites tumor cells, but it required 150 μg per ml for abrin‐b. Both these two proteins at a sublethal dose could inhibit the growth of Ehrlich ascites tumor cells which were injected simultaneously with these proteins. 131I‐abrin‐a and 131I‐abrin‐b were able to bind Sarcoma 180 cells, and the binding of abrin‐a could be inhibited by lactose, raffinose, galactose and rhamnose, but none of 15 sugars tested inhibited the binding of abrin‐b.