Treatment of Grass Land for Elimination of Disease. 79 



conditions obtain, may become a source of pollution of pastures 

 and stock. It is, therefore, in this relation advisable to 

 introduce only animals from uncontaminated sources ; but while 

 the attainment would be ideal, it is to be feared that no such 

 assurance is to be acquired, and that in the purchase of fresh 

 animals some degree of risk must be accepted. 



As most of the diseases to which live stock are liable occur 

 in animals at grass, it will be evident that limitations of space 

 will admit of but cursory treatment of the subject, and all that 

 can he attempted is a glance at what we regard some of the 

 more salient features in certain of its aspects. 



The contamination of grass land, which is frequently 

 referred to as " soiled," " tainted," or " sick," has, owing to 

 heavy losses of stock, particularly of sheep, at pasture, been 

 much under consideration for the past quarter of a century. 

 As the terms imply, the condition occurs where large numbers 

 of animals have been more or less continuously grazed for 

 prolonged periods in relatively small areas. It would appear 

 that the expressions are not infrequently employed to convey 

 the idea that the unhealthiness of the pastures and unthrifti- 

 ness and disease of animals grazed on it are directly due to the 

 nature and quality of the herbage produced under the foregoing 

 circumstances. Indeed, one has often heard expressed the 

 belief that the chemical constitution or physical state of the 

 grass is at fault, and that it lacks some of the elements 

 essential to the physiological requirements of animals of the 

 class for which a pasture is said to be " sick," and so is the 

 direct cause of " pining and sickness." The feeding qualities of 

 grass land, it must be allowed, may be rendered more or less 

 ap})ropriate by treatment depending on the habits of various 

 species of animals or by its management, but we know of no 

 solid reason for thinking that the composition of grass can be so 

 altered by any form of treatment as to render it, of itself, capable 

 of inducing disease. The "sickness" of pasture is usually, 

 if not exclusively, due to its pollution by some living germs of 

 disease emanating fx-om animals. In our experience the 

 " tainting " of grass land is most commonly met with under 

 circumstances known to be favourable to the existence of 

 parasitic worms on pastures, and in the investigation of 

 illnesses and fatalities among grazing animals on land said to 

 be "sheep sick," "horse sick," &c., such occurrences have 

 been most frequently found due to the attack of parasitic 

 worms. The adoption of measures for the elimination of such 

 diseases must be influenced by consideration of points in the 

 life histories, as far as they are known, of the parasites which 

 cause them. The contamination may consist solely or mainly 

 of parasites of one or more species or variety. It is a common 



