Hæmatozoa

[Gr. haima, blood, zoon, a living being.] ( Zool.) A term applied to the animalcules, or entozoa, which exist in the blood of mammals, birds, reptiles, fishes, and many invertebrate animals. They are generally microscopic, without generative organs, and found existing in the blood circulating both in the arteries and veins. A very small proportion attain a large size and have organs of reproduction; these are generally found in some special part of the body. Thus the variety called Distoma hæmatobium is only found in the abdominal venous system; another variety is found restricted to the abdominal arterial system of the horse; and the Pseud ali us filum is only found in the pulmonary artery and branches of the porpoise. Very little is known concerning the origin of these entozoa. It seems probable that some of the minute forms are the larvæ of worm living in the organs surrounding the ve els. The most important of the human hæmatozoa is the variety mentioned above; it has only been observed in Egypt. The liver-fluke, Distoma hepaticum, has sometimes been found in the interior of the portal vein. Those hæmatozoa which have been found in tumors must have been conveyed there by the blood. Horses and dogs are frequently affected with these parasites; in the case of the latter animal, they are seldom large enough to be visible to the naked eye. The presence of hæmatozoa does not, however, seem to affect the general health of either men or the animals.