326 PARASITES OF ANIMALS 



three and four millions of individualised life-forms, whilst the 

 solitary sheep itself would, under the same circumstances, be the 

 means of causing the production of at least 3,000,000,000 fluke 

 zooids ! Happily, no such results as this can possibly occur in 

 nature, since interfering agencies reduce the favorable conditions. 

 However, the balance of parasitic forms from all sources is 

 usually sufficient to destroy thousands of sheep annually. The 

 virulence of rot-epizooty is entirely due to the presence of con- 

 ditions favoring the development of fluke larvae. 



As regards the injurious action of this parasite on animals, 

 it is well known that in particular years, in England alone, 

 hundreds, and even thousands, of sheep have been destroyed in a 

 single season. A writer in the ' Edinburgh Veterinary Review ' 

 for 1861 states that in the season of 1830-31 the estimated 

 deaths of sheep from rot was between one and two millions. 

 This would, of course, represent a money loss of something like 

 four million pounds sterling. As affording additional striking 

 instances of the disastrous effects of rot, I may cite the statements 

 of Davaine. Thus : " In the neighbourhood of Aries alone, 

 during the year 1812, no less than 300,000 sheep perished, and 

 at Nimes and Montpellier 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." 

 In like manner our English authority, Prof. Simonds, fur- 

 nished 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, com- 

 pelling 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. 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 



