FASCIOLA HEPATICA 153 



These periods are sometimes very marked, but at others, owing to 

 subsequent * infestations, the features become merged and so 

 obliterated. But when a single infestation occurs they are very 

 marked. 



The first period is called the PERIOD OF IMMIGRATION. This 

 occurs at the fall of the year and generally passes unperceived, as 

 the young flukes do little harm to the liver. It varies from four 

 to thirteen weeks. Gerlach has remarked upon cases of death 

 from apoplexy at this period. 



The second period is the PERIOD OF ANEMIA. This occurs in 

 November and December. The sheep at first fatten rapidly, but 

 later their mucous membranes become pale and of a yellowish hue, 

 and they become sluggish and cease to feed. The faeces are normal, 

 but may contain fluke ova. 



b. 



FIG. 86. Egg of Fasciola hepatica, L. FIG. 87. Limnceus minutus, the inter- 



240/1. At the lid-end the yolk cells may mediary host of the Liver Fluke, a, natu- 

 be observed through the shell. ral size; b, magnified. (From Leuckart.) 



The third period is the PERIOD OF WASTING. This corresponds 

 with the beginning of January about three months after the 

 entry of the larva?. Emaciation now becomes very marked, the 

 skin and mucous membranes blanched, temperature variable and 

 marked by an- irregular curve ; respiration laboured and quick ; 

 appetite regular ; abortion frequently occurs in pregnant ewes ; 

 pressure on the back causes the animals to fall ; local oedemas 

 occur, the most perceptible in the submaxillary space, extending 

 below the larynx and over the cheeks and parotids (called 

 " bourse," " boule," in France ; " watery poke " or " cockered " in 

 England). Death usually occurs at this period, but a fourth 

 stage may occur. 



The fourth period is the PERIOD OF EMIGRATION OF THE 

 FLUKES, This is a period of convalescence and recovery, generally 

 in May and June. F. V. T.] 



