2o 4 VETERINARY LECTURES 



greater numbers may be hatched, and still more in June and July. These two 

 months are the time of the year when the country is most liable to be infested by 

 snails. As more eggs are distributed through the whole of the summer by fluked 

 animals, it is clear, of course, that the production of embryos, though in less 

 numbers, will continue from August until the time when the development is 

 checked by autumnal cold. June and July, then, are the principal, but not the 

 only, months in which we are to wage war against the embryos; the latter part of 

 August, September, and October, are the months in which especially to destroy 

 the germs on the grass ready for transference to the sheep.' 



312. In the autumn, the snail Limnmis truncatulus, just before 

 going into its winter-quarters — i.e., burying itself in the mud — may 

 become infested with one or more embryos, and, for the want of heat, 

 their further development is arrested until spring, when the rays of 

 the sun bring the snail to the surface of the ground, and the various 

 transformation stages of the embryo fluke is then carried on, always 

 provided heat and moisture are present. This, to my mind, is the 

 greatest cause of the infection. The eggs deposited by the mature 

 flukes in the liver, and again deposited on the ground in the winter 

 months, are in great danger of being destroyed by the want of heat to 

 germinate the embryo, as well as by the absence of its intermediate 

 host, the snail, which is in its winter habitat. Sometimes, however, 

 too many embryos enter one snail, and this results in not only 

 the death of the host, but in their own as well. As may be inferred 

 from the foregoing extract, the disease is not so rife in dry seasons, 

 but is very common after wet summers. Animals may be affected 

 as early as midsummer, but August, September, and October are the 

 principal months for contamination ; and as it takes ten or twelve 

 weeks after the entrance of the pupce into the liver before any bad 

 effects are noticed, December, January, and February are therefore 

 the chief months in which flukes are to be seen fully matured. The 

 fluke has been proved beyond all doubt to be a fresh-water creature, 

 and, as mentioned previously, the disease is never met with on salt 

 marshes. Therefore, the land should be dressed in autumn and 

 spring with salt, the first application being to destroy the snails 

 before they seek their winter shelter, and the latter to annihilate any 

 who may have escaped the previous dressing, as they come to the 

 surface of the ground ; even a weak solution — viz., 1 ounce of salt 



