66 



The Rot in Sheep. 



Sthenic diseases as a rule, and especially those centered in the 

 more important organs of the body, are accompanied with such 

 well-marked peculiarities, that the practitioner rarely fails in re- 

 cognising either their nature or seat. Asthenic maladies, on the 

 contrary, are often attended with such general or ambiguous 

 symptoms, that even the most experienced pathologist may, at 

 the outset, fail to determine their true character, or the precise 

 cause on which they depend. Affections of internal organs, 

 which commence with only a slight impairment of function, due 

 to a hidden or unknown cause of irritation, are of all others the 

 most difficult to diagnose. Among these may be named several 

 of the parasitic maladies, of which rot in sheep may be taken as 

 an example. Even in those instances where no difficulty really 

 exists with regard to the time of the reception of rot, we 

 often look in vain, for many weeks, for clear evidence of its 

 existence. 



Simon, in his 6 Lectures on General Pathology,' delivered at St. 

 Thomas's Hospital in the session of 1850, rightly remarks that 

 " if you examine parasitic diseases from first to last, you will 

 find that they are, perhaps of all known maladies, the most essen- 

 tially local. They may be very extensively diffused- — may be in 

 very many spots of the body — and the sum total of many small 

 irritations may be a large general irritation ; or if the parasites 

 are large as well as numerous, they may drain the system of 

 blood, and anaemiate and kill the animal, as we see in the rot of 

 sheep. But all we know of parasitic influence on the health — 

 and I may observe that a good deal is known — all, I say, is 

 referable to these two heads : local inconvenience from pressure 

 or from irritation ; general inconvenience, either febricular, from 

 that local irritation becoming inflammatory, or anaemiative by 

 draining and impoverishment of the blood." 



The latent stage of rot — viz. the period which elapses between 

 the entrance of the penultimate forms of the fluke into the 

 system, their change into perfect flukes and acquirement of 

 sufficient size to begin to drain the organism — is the one which 

 perhaps interests the pathologist more than any other. He sees 

 in it the gradual development of causes which he would fain 

 interpose to arrest : because, if unchecked, he knows they must 

 ultimately undermine the constitution. But he is without suffi- 

 cient warrant to take action, in so far as the animal itself is 

 concerned, for he can recognise no symptoms of confirmed ill- 

 health. In some instances, however, practical knowledge comes 

 to his assistance, and when he finds animals surrounded by cir- 

 cumstances which experience has proved will engender rot, he 

 does not hesitate to have recourse to prophylactic measures. 



The latent stage of the disease is also the one of the first 



