74 Treatment of Grass Land for Elimination of Disease. 



of land under corn-crop has decreased by 2,000,000 acres, 

 and that under roots by 400,000 acres, while that of 

 " permanent pasture " has increased by about 3,000,000 

 acres, the number of cattle by 1,300,000 head, and of sheep 

 by 2,000,000 head. Live stock has become the more impor- 

 tant element in the consideration of British agriculturists, 

 and this, in conjunction with increased facilities for dis- 

 semination of agricultural news, probably tends to bring 

 under notice more than formerly the occurrence of disease in 

 individual cases. The older literature of the subject is often 

 misleading and does not always afford safe ground for 

 comparison. For instance, Youatt, writing about seventy 

 years ago on '' The Sheep," refers to " consumption," 

 " diarrhoea," and " dysentery " as responsible for serious losses 

 in his day. More recently acquired knowledge, admitting 

 of the study of diseases in relation to their causes, allows 

 UB to arrange them more precisely. To-day it is known 

 that, while sheep are susceptible to tuberculosis, to which 

 Youatt's description makes it clear he refers as " consump- 

 tion," they are extremely rarely affected with it under the 

 conditions in which they have always lived in this country. 

 Excepting the " mysterious worm in the foot," the fluke and 

 the gid-hydatid in the brain are the only worms to which 

 reference is found in the index of this work ; yet his 

 description of symptoms, post-mortem appearances, and cir- 

 cumstances under which the diseases occurred make it fairly 

 clear that all three conditions referred to under the foregoing 

 names are now very common and known to be due respectively 

 to worms in the lungs, stomach and intestines. There are, 

 however, cogent reasons for thinking that altered management 

 of our live stock consequent on change of circumstances has 

 conduced to the more frequent occurrence of disease in serious 

 form in animals on our grass lands, and, while to-day we may 

 possibly encounter some diseases of animals unknown in this 

 country a century ago, it is beyond doubt that the ploughing 

 and cultivation of land have, in a general way, a purifying 

 effect, and that the prolonged absence of animals must 

 materially lessen the risk of its becoming contaminated and 

 remaining so. 



It is notorious that grazing animals are more liable to 

 disease in some situations than in others. Fields and farms 

 may acquire the reputation of being healthy or unhealthy to 

 animals of one or more species. Holdings are advertised as 

 "sound" or healthy for all or certain classes of stock and 

 valued accordingly. From time immemorial it has been 

 customary to associate certain diseases with certain grass 

 lands, often under the conviction that such diseases are 



