TJie Rot in Sheep. 



21 



for their close biting, for which their lips and incisor-teeth 

 are beautifully adapted, and hence their greater exposure to the 

 cause of rot than the ox which crops the longer grasses. Hold- 

 ing the opinion which we do that rot is none other than an 

 entozoic disease, referable to the entrance of the penultimate 

 forms of the liver-fluke into the digestive system of the sheep, 

 we conceive that an explanation is to be found in the circum- 

 stance that these infusorial animalcules mostly abound at the 

 lower portions of the stems of the grasses — the parts eaten by 

 the sheep — than elsewhere on the plants. 



Cleeve, in his Essay on the Diseases of Sheep, published in 

 the first volume of the Journal of the Royal Agricultural Society, 

 p. 310, narrates a fact singularly corroborative of the opinion 

 we have expressed. He says that in the parish of Seaton, in 

 Devonshire, all the sheep that were depastured in the marshes 

 one year were attacked with rot and died, only excepting four ; 

 on examining these four, it was found that they were hog-jawed, 

 and, from the under jaw being much shorter than the upper, 

 they could not bite near the ground." 



We may here leave the further consideration of this question 

 for the present, and proceed with the history of the assigned 

 causes. 



In the year succeeding the publication of Mr. Youatt's work 

 a small manual on the diseases of sheep made its appearance, 

 from the pen of Mr. A. Blacklock, surgeon, Dumfries. This 

 gentleman strongly repudiated the opinion of entozoa being the 

 cause of rot, and considered that the malady arose solely from 

 tubercles located in the lungs. He remarks that " everything 

 that has a tendency to weaken the animal will more or less lead to 

 rot. Exposure to cold and wet, mishaps at lambing-time, food 

 bad in quality or deficient in quantity, and over-driving, will 

 all predispose the constitution to the deposition of tubercles." 

 Hereafter we shall have occasion to recur to the writings of 

 Mr. Blacklock, and will therefore only now incidentally remark 

 that the so-called tubercles in the lungs of sheep have no patho- 

 logical relation to those met with in cases of phthisis of man. 

 Since the period at which this gentleman wrote, it has been 

 ascertained that these deposits are produced by the well-known 

 entozoon, the Strongylus filar ia. 



Subsequently to this date we do not find that any author of 

 note has propounded such a peculiar idea of the cause of rot. 

 Mr. Spooner, of Southampton, however, after reviewing the 

 statements of others with reference to the several causes of the 

 disease, in his History, Structure, Economy, and Diseases of 

 Sheep, 1844, remarks, " it appears to me that, in addition to 

 the consumption of food in which water greatly abounds, it 



