[The economic margins of activities of a bovine practitioner on dairy farms].

Because of lower margins and market liberalisation veterinarians and farmers are increasingly negotiating rates. Therefore, the margins of veterinarians are under pressure. In addition, the sales if drugs, performance of operations or giving of advice are more and more separated.

[Post-mortem findings in seals which died in nature (author's transl)].

The findings in seals submitted to the Research Institute for Nature Management, Arnhem, for post-mortem examination during the period from 1960 to 1981 are reviewed with reference to three tables. A striking feature was the large proportion (55 per cent) of young seals, well over 38 percent of which died in the first two months of life. There also was a large proportion of young seals and yearlings with parasitic infections, which would appear to suggest that it is difficult for the young animals to build up a good condition.

Mercury and selenium in marine mammals and birds.

Information is provided concerning the concentrations of mercury and selenium in tissues of marine animals. In marine mammals a 1:1 Hg/Se molecular increment ratio was found and an almost perfect linear correlation between mercury and selenium. It is suggested that marine mammals are able to detoxify methylmercury by a specific chemical mechanism in which selenium is involved.