172 ENTOZOA. 



liver-leech plague ; in systematic works, however, it is emphatically 

 denomiaated die LeberJcrankheit, or Fclule. 



As instances of its disastrous effects upon the revenues of 

 agriculturists, we may cite the statements of Davaine, as suc- 

 cinctly quoted by Leuckart, and also individual cases recorded by 

 Simonds. " In the neighbourhood of Aries alone, during the 

 year 1812, no less than 300,000 sheep perished, and at Nimes and 

 Montpelher 90,000. In the inner departments, during the epidemic 

 of the years 1853-54, many cattle-breeders lost a fourth, a third, and 

 even three-fourths of their flocks." On the same score, our English 

 authority furnishes a variety of painful cases. Thus, on the estate 

 of Mr. Cramp, of the Isle of Thanet, the rot epidemic of 1824 

 " swept away £3000 worth of his sheep in less than three months, 

 compelling him to give up his farm." Scores of cases are on 

 record where our English farmers have individually lost three, four, 

 five, six, seven, and even eight hundred sheep in a single season ; 

 and many agriculturists have thus become completely ruined. 



Remarkable periodic outbreaks of this disease are recorded by 

 Simonds as occurring in England in the successive years of 1809, 

 '16, '24, '30, '53, and '60; whilst, for France, Davaine mentions 

 1809, '12, '16, '17, '20, '29, '30, '53, and '54 as the most remark- 

 able years. It would be interesting to know how far these out- 

 breaks tally with the similar outbreaks which have occurred in 

 Holland, Germany, and other European districts ; for, even here, 

 we perceive that the disease was prevalent during four separate 

 years in France and England at one and the same time. This, 

 indeed, is no more than we would naturally expect, considering 

 that the extent of the development of the larval forms must, in a 

 great measure, be dependent upon atmospheric conditions. A 

 warm and moist season would alike prove beneficial to the develop- 

 ment of the larv83 and their intermediate molluscan hosts. Their 

 numbers would also multiply enormously ; for, as Pagenstecher has 

 shown, the degree of non-sexual production of trematode larvae 

 within their sporocysts is materially affected by atmospheric 



