ON PARASITES. 9 



parasite will be noted hereafter. Seuckart says : "Whenever an animal 

 is too small and too imperfectly armed to overawe and destroy that 

 which its instinct leads it to seek for nourishment, it must be content 

 with robbing it by feeding upon its juices and solid parts." Thus 

 the sheep in pasturing in certain localities swallows unconsciously a 

 dreadful enemy — the six-hooked embryo of the Coenurus cerebralis 

 encased in its coat of mail : for such in truth may be called in its 

 particular case the eggshell in which it is securely developed, amid 

 the hazardous vicissitudes to which it is exposed, Set free from this 

 ovular envelope by the action of the digestive juices in the alimentary 

 canal, the coenurus commences an active-passive migration to the 

 brain, where it causes the disease well known as the " staggers," from a 

 prominent symptom manifested. The disease called the " measles" 

 in the hog depends upon a similar cystic worm the cysticercus 

 cellulosae. Carnivora like the wolf, the dog, and man himself, feeding 

 upon the^e infected herbivora, become themselves infested with tape 

 worms. 



Prom the preceding observations it maybe gathered, that parasites 

 exert a very decided influence over man's natural well-being, through 

 their ravages upon his means of support. Yet the discoveries that 

 have been made regarding them are among the crowning triumphs of 

 the scientific skill, industry, and acumen of the observers of the 

 present day, in contradistinction to those of the past. 



But still farther. The science and the art of medicine have for 

 many centuries been cultivated with zeal and assiduity by a class of 

 men who specially devoted their attention to the subject. The dis- 

 eases which affect the human frame have always been regarded as 

 worthy of special attention, and honors and emoluments have been 

 heaped upon the successful physician. But strange to say, until the 

 present century the parasites infesting the human subject remained 

 in almost total obscurity. By some fatality the small number of 

 disconnected facts with which the elder physicians were familiar, re- 

 ceived a false interpretation. Their production, mode of nutrition, 

 and anatomy, were all misunderstood, and the symptoms supposed to 

 indicate their presence were vague, trivial and incongruous. There 

 was a general opinion among medical men of their vast abundance 

 which, as may be easily imagined, found an exaggerated reflection 

 among the laity. In fact ivorms were the bugbear of old women and 

 anxious mothers. Even at the present day the physician who prac- 



