DISEASES OP THE BLOOD. 183 



others, promise to elucidate our pathology of these disorders, 

 and to explain occasional or regular access of intensity of 

 febrile diseases. Spirilla are corkscrew-shaped organisms, 

 which occur in the blood in intermittent fevers ; they were 

 considered special life phases of bacteria; by observers of 

 high standing they are thought to be nematodes. Manson 

 notes that they are absent from the blood of the patient 

 during midday, but are generally diffused through that fluid 

 at night, when their intermediary bearers, the mosquitoes, 

 are actively blood-sucking. We have already observed 

 that disorders of this intermittent character affect the ox, 

 especially in low lying, marshy places. Quinine is the 

 most useful of the antiperiodic agents suited for these 

 cases. 



Parasites in the blood, or which are distributed through- 

 out the system by the blood, and thus are found in many 

 parts of the body. — Haematozoa, parasites whose habitat is 

 the blood, though frequent in some animals, have not yet 

 been observed in the ox. Many entozoa are supposed 

 when immature to enter into the blood, and by that fluid 

 to be carried to their special habitats, and when they 

 arrive there instinctively to migrate through the walls of the 

 blood-vessels, just as we may imagine the contagia of specific 

 eruptive disorders do in selecting special membranes as their 

 seat of lesion. Of these we need only instance Strongylus 

 micruruSy the producer of parasitic bronchitis. Other 

 entozoa are carried in an immature condition indifferently 

 to various tissues. Of these the most important clinically 

 is Echinococcus veterinorum, the cystic phase of Taenia 

 echinococcus of the dog. 



Echinococcus Disease is especially prevalent in certain 

 localities, as, for instance, the Yale of Aylesbury, and con- 

 sists in the growth in certain organs, notably the lungs 

 and liver, of cysts, frequently multilocular, and always 

 enclosed in a dense capsule and filled with a watery fluid. 

 The true cysts is thin- walled, of a pure white colour, and 

 soft. As these grow very gradually they cause little, if 

 any, functional disturbance, so that often their presence is 

 not even suspected, the bearer being slaughtered, and the 



