DISTOMATOSIS — LIVER FLUKE DISEASE — LIVER ROT. 



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enormous number (37,000 to 45,000) of eggs. This unusual fertility of the 

 parasite is necessary because of the complicated life history and the com- 

 paratively small chance any one egg has of completing the entire cycle. 



Hosts. An interesting and, from an agricultural standpoint, an 

 important matter connected with this fluke is that it is found in a large 

 number (about twenty-five) of domesticated and wild animals, and this 



Fig. 157. — Drawing from a microscopic preparation, showing the glandular hyper- 

 plasia of the mucosa of a gall-duct caused by the common liver fluke {Fasciola 

 hepatica). a, Hypertrophied submucosa ; b, interstitial connective tissue; c, com- 

 pressed lobule ; d, lumen of the gall-duct — thickened fibrous wall of the gall-duct. 

 (After Schaper, 1890, PI. I., Fig. 2.) 



fact probably explains to some degree the wide geographical distribution 

 of the parasite. 



Symptoms. The symptomatology of this disease may clinically be 

 divided into three well-marked periods : 



I. Primary period. The primary phase commences with the pene- 

 tration of the embryos of the parasite into the body, firstly into the 

 intestine, and then into the liver by ascending the bile ducts. This phase 

 occurs during the last months of the year, October, November, and 

 December, and is rarely accompanied by alarming symptoms. At this 

 time the sheep appear in good health, the summer being over, and the 



