i9o6.] 



LOUPING-ILL AND BrAXY. 



of the louping-ill bacillus added to it, and the mixture incu- 

 bated at the body temperature with exclusion of air, very 

 opposite results were obtained at different seasons of the year. 

 If this were done in the spring, during the louping-ill season,, 

 the organism, as a rule, grew freely upon the blood, while at 

 other times of the year the converse usually took place— the 

 blood destroyed the bacillus. A period was eventually reached^ 

 in July and August, when this bactericidal action of the blood 

 became complete and invariable. 



The same remarkable fdct was found to apply to the bacteria 

 of a number of allied diseases to which further reference will be 

 made. 



A clue to the whole nature and cause of the disease had now 

 been obtained. During certain months of the year the louping- 

 ill bacillus may apparently reside and multiply in the alimen- 

 tary canal without occasioning any injury to the sheep. The 

 wall of the stomach and of the intestine forms a complete 

 barrier to its passage into the peritoneal cavity or into the 

 tissues. This seems to be due to the blood exerting an influence 

 inimical to its growth at these particular times. When the 

 dangerous period, viz., the spring time, approaches, owing to the 

 |)lood failing in its power to destroy the bacillus, this protective 

 influence is lost, and the organism, if now picked up by the 

 sheep for the first time, is able to pass the wall of the intestine 

 with facility. If such be the case, the growth in the peritoneal 

 liquid will be luxuriant, the liquid turbid from the multitude of 

 bacteria present, and the sheep will die with symptoms of blood 

 poisoning. 



It can well be imagined, however, that there may be many 

 cases where the power of the blood is not so completely lost, 

 and that under such circumstances the invasion of the cavity 

 would be much more gradual. A condition of chronic poison- 

 ing would then be established, the poison acting slowly on the 

 nerve centres and paralysing them. This gives rise to the 

 second kind of case, where the disease seems to run a chronic 

 course, and where nervous symptoms are manifested. It is in 

 this type of the disease that the peritoneal liquid is usually 

 clear, and the bacilli so few as to be unrecognisable under the 

 microscope until their numbers have multiplied by incubation. 



