As in human pathology this condition may be divided into the group that follows some disease which damages the red blood cells or their source, called secondary, and those cases not preceded by such a condition, called primary. Formerly this latter group, known as progressive pernicious anemia, was copiously represented, but study has discovered that worms, inorganic poisons and infections can produce a picture of grave anemia so that the formerly large group has dwindled. We now conceive a primary anemia to be one without discoverable responsible antecedent pathology, therefore a disease of the bone marrow itself. There is one variety, hemolytic anemia, which seems to be an intoxication of the bone marrow with solution of red cells, but the affected tissue puts up some struggle against the poison. In another primary, the so-called aplastic anemia, no activity at all is shown by the marrow, no young cells appearing in the circulation. Clorosis, or green sickness of young persons, is a primary anemia and presents itself as a moderate cell reduction with a disproportionately low hemoglobin percentage. As a disease entity this does not occur in the lower animals, so far as I am aware, but a very few hemoglobin estimations and a reference to the literature would indicate that well marked hemoglobin anemia does occur. In so far as the pathology of anemia is concerned we are obliged usually to judge by the appearance of the blood and tissues, the yellowish pallor of the mucous membranes, the condition of the marrow and the amount of pigment; severe rapid cases show hemorrhages and prolonged cases have fatty degeneration of the parenchymatous organs. For a decision of the primary or secondary nature we must judge the accompanying pathology and the condition of the bone marrow. SECONDARY ANEMIA. Secondary anemia can be laid in general to insanitary housing or inappropriate diet over a long period, to chronic bacterial infection of low grade, to the action of blood parasites or those of the bowel which either suck blood or elaborate an absorbable toxin, or to single great or repeated small hemorrhages. We shall now consider the cases at the Garden. Perhaps many other animals have had a substandard blood, but these are the cases in which the gross appearance attracted close scrutiny in this direction. London has had much anemia, probably from their reported heavy infestation with parasites, but this factor has with us apparently played a small rôle in the production of anemia. IN MAMMALIA.