120 ENTOZOA FOUND IN MAN. 



Chapter XV. 



THE ENTOZOA EOUND IN THE SANGUINEOUS 

 SYSTEM :— HCEMATOZOA. 



The existence of worms in a free state in the blood- 

 vessels of certain animals is a fact which has 

 long been recognised ; and these parasites have been 

 united into a distinct group, and described under the 

 name of Hoematoza. 



They have been found in mammiferae, in birds, 

 reptiles, fishes, and several invertebrate animals. 

 The majority of them are of microscopical size, and 

 circulate with the blood through the vessels ; a few 

 species only are provided with reproductive organs, 

 and attain to more considerable dimensions, and these 

 are generally confined to special parts of the san- 

 guineous system. 



Their origin is, like that of many of the other en- 

 tozoa, not yet known. Even if we suppose that those 

 wliich possess reproductive organs are developed in 

 the cavity which they inhabit, the question will arise 

 how they are transmitted firom one person to another, 

 and also why it is that their number is usually 

 limited, although their ova or their larvae may exist 

 in considerable quantity. 



Some observations which have been recently 

 made tend to show that some of the species 

 of hoematozoa which are unprovided with reproduc- 

 tive organs are the larvae of worms which live either 

 in the vessels or in the viscera of the animal in 

 which they are found. 



