PARASITIC DISEASES OF THE LIVER 313 



The cause of this morbid action is not very clearly understood. It 

 is known to have followed severe exertion, as after a good burst of speed 

 in the hunting-field, but the writer has known it to occur in the stable 

 after days of idleness, and on one occasion to usher in an attack of colic. 



The suddenness of its onset and disappearance, and its behaviour while 

 present, seem to mark it out as a neurotic affection, in which the pneumo- 

 gastric nerve is most likely specially concerned. 



Treatment. — Diffusible stimulants with anodynes, enjoined with warm 

 clothing to the body, are measures most likely to subdue the morbid 

 activity of the muscle. These should be followed by a dose of aperient 

 medicine and a short period of careful dieting. 



PABASlTlC DISEASES OF THE LIVER 



These happily are not numerous in the horse. The chief offenders are 

 the " distomes " or flukes, and the " cestodes " or bladder-worms. Of the 

 former the Distoma hepaticum, fig. 112, 

 is the particular species which infests the 

 liver of the horse. Of the latter the 

 Eclmiococcus veterinorum, fig. 113, the 

 cystic or bladder phase of development 

 of the Tcenia echinococcus of the dog, 

 is the principal, if not the only hydatid 

 parasite infesting the liver of this animal. 



The Distoma hepaticum in its em- 

 bryonic condition gains access to the body 

 by means of food and water, and, having 

 reached the small bowels, enters the liver 

 by way of the biliary duct. Here it 

 takes up its abode, and in the course of 

 its growth and development excites irrita- 

 tion in the bile-ducts, leading to thicken- 

 ing and disorganization of their walls, 

 blocking up of the biliary channels, and 

 interruption to the proper discharge of the 



bile into the alimentary canal. When the parasites exist in consider- 

 able numbers the structural changes extend beyond the ducts into the 

 parts around, where an active growth of connective tissue is induced. 

 As a consequence of this the blood-vessels are compressed, the circulation 

 is interfered with, the glandular tissue suffers impairment of nutrition, 

 and its destruction sooner or later follows. Should this destructive 



A, Showing anatomical details. B, Natural 

 ;e. c, Ciliated embryo or young distome. 



