LOUPING-ILL. 



431 



valleys of Dumfriesshire. It is rare in Berwickshire, common in 

 the north and west of Eoxbm'ghshire and the similar hilly districts 

 of Selkirkshire and Peeblesshire. It occurs in Ayrshire, to a slight 

 extent in Lanarkshire, and is found in the western parts and islands of 

 Argyleshire and Inverness-shire. 



Not only is the disease very circumscribed in its distribution as a 

 whole, but locally in the places mentioned infected and non-infected 

 spots are pointed out. These may be quite contiguous. The flocks in 

 the North Tyne district feed up and down the hills in limited " cuts," 

 and it is one of the features of the illness that certain " cuts " are very 

 liable to it, while others, even on the same farm, are just as free. In 

 many cases the nature of the pasture is such as to suggest to an ex- 

 perienced man the probability of its being subject to the disease. A dry 

 and foggy pasture seems best suited for harbouring the cause of the 

 malady. These infected places have remained wonderfully constant, but 



Fig. 198.— Larva of the 



grass tick. 



Length, jV^"!^ °f 1 inch. 



Fk;. 199. — Pupa of the grass tick. 

 Length, f^th of 1 inch. 



a peculiar feature about them is that some may be very bad for louping- 

 ill one year, and others bad another year. Of two adjoining farms, one 

 may be badly attacked and the other mildly, while in the following year 

 the conditions may be reversed. Districts may present the same pecu- 

 liarities. Thus, though the disease is essentially endemic, it is not abso- 

 lutely constant in its recurrence. There seem to be certain circumstances 

 capable of favouring or retarding it. 



Lesions. The chief lesions are localised in the membranes of the 

 brain and spinal cord, which are congested or inflamed, and contain an 

 increased amount of cerebro-spinal fluid or a jelly-like, sometimes blood- 

 stained exudation. Softening and hardening of the spinal cord have both 

 been observed. Inflammation of the pleura and pericardium, with fluid 

 or jelly-Uke exudation, are common ; lobar congestion of the lungs, endo- 

 carditis, gastritis, and enteritis have all been described ; some observers 

 have mentioned congestion of the kidneys and liver and swelling of 

 the spleen. Lesions of the nerve-centres are the most constant and 

 reliable. 



