1 84 LEISURE-TIME STUDIES. 



prevail to an alarming extent. Hidden enemies in the sea 

 burrow into the sides of ships, or undermine man's piers 

 and bulwarks. Poison-traps lie in wait for human footsteps ; 

 and claw and tooth are as ruthless when opposed to humanity 

 as when prepared to attack lower life. Speaking generally, 

 therefore, man may be readily shown to be by no means the 

 undisputed " monarch of all he surveys " in the territory of 

 either botanist or zoologist ; and the province of mind and 

 intellect may be invaded by foes against which man may 

 find it impossible to contend. Much has been done, it is 

 true, in the way of repressing many of our lower enemies, 

 and the increase of scientific knowledge has had few triumphs 

 of higher kind than are witnessed in those researches which 

 have exposed the nature of our animal and plant enemies, 

 and shown us the steps necessary to be taken for their 

 annihilation. But the field of inquiry seems well-nigh 

 boundless ; and it should certainly form one of the most 

 powerful arguments in favour of the study of natural science, 

 that on the advance in our knowledge of economic botany 

 and zoology the prosperity of our commerce and the conser- 

 vation of our health may be shown largely to depend. 



Perhaps one of the richest fields of research in the way 

 of repression of our lower enemies, is offered by the life- 

 history of some of the most common parasites which deci- 

 mate our flocks and herds, and which, as already remarked, 

 occasionally invade the human territory itself. Well does 

 the shepherd know the symptoms of " rot " in his flock, and 

 anxiously does he apply to the veterinarian for advice in his 

 extremity. His sheep, in such a strait, present a dull and 

 dejected appearance ; they are " off their feed," he will tell 

 the observer ; and are in a thoroughly emaciated condition, 

 despite the shepherd's kindly care and supervision. By-and-by 

 deaths will begin to be of frequent occurrence, and when 

 the dead subjects are carefully inspected the cause of the 

 disorder is not hard to discover. The body of the affected 

 sheep exhibits a state of thorough disorganisation, and when 

 the liver is carefully inspected, hundreds of small flattened 



