418 TRANSACTIONS OF SECTION D. 



MONDAY, SEPTEMBER 4. 



The following Papers were read : — 



1. Notes on a Trypansome found in a Sheep Tick, and its probable connection 

 ivith the Disease known as Louping-ill. By Major C. F. Bishop, R.A. 



In previous investigations of louping-ill many possible causes have b:en sug- 

 gested, tested, and either discarded or left unproven. 



Until 1902 a considerable amount of attention was paid to the ' Tick Theory,' 

 which held that, as louping-ill appears and disappears at approximately the 

 beginning and end respectively of the sheep tick season, there was great prob- 

 ability that the ticks were closely connected with the propagation of the disease. 



In December 1901 the Board of Agriculture appointed a Committee to inquire 

 into the causes of both louping-ill and braxy, and after four years of investiga- 

 tion and experiments the Committee issued a lengthy report in 1906, announcing 

 that they had discovered, and proved, the cause of louping-ill to be a bacillus, 

 which during certain months of the year, namely, April and May. attacks the 

 intestine of the sheep, thereby causing the disease, although during other 

 months the sheep's blood is able to resist the harmful powers of the germ. 



The Committee also announced that they had inquired into and tested the 

 ' Tick Theory,' and had come to the conclusion that it was quite untenable. 

 They sum it up as the sort of unscientific suggestion that farmers would natur- 

 ally make, founded upon the mere coincidence that ticks and louping-ill often 

 occur together. 



This report has, since 1906, been the last word on louping-ill j the established 

 truth concerning the disease. 



Early this year, at the suggestion of Professor Meek, F.Z.S., who in 1896 

 and ±897 was a strong upholder of the ' Tick Theory,' the writer began a small 

 investigation of louping-ill, with the idea of searching for some blood parasite 

 which might prove to be the true cause of the disease, and spent five days at 

 a farm in the louping-ill district, near Bellingham, collecting ticks off diseased 

 sheep, and specimens of blood taken direct from the living animals, or from their 

 internal organs after death. 



The first result obtained was the discovery of a trypansome, on a slide made 

 of blood squeezed from a tick, taken off a sheep, said to be a typical case of 

 louping-ill. 



The trypansome lay in a good position on the slide, and had stained excel- 

 lently with Leishman's stain. Its dimensions are : Length (in a straight line), 

 21'75 microns; greatest breadth, 1*5 micron j nucleus, length, 3 microns; breadth 

 1 micron ; centre of nucleus, 9'75 microns from posterior extremity ; the blepharo- 

 plast is large, and lies anterior to the nucleus. 



No trypansomes having yet been found in any of the sheep examined, there 

 is no proof that the one found in the tick had been sucked from a sheep; but, 

 from the frequent association of these parasites with diseases in horses and 

 cattle, there is a probability of its being connected with the disease of the sheep. 



The next result obtained by the author was the discovery of certain forms, 

 apparently blood parasites, in a specimen of blood from the sheep off which 

 the tick containing the trypansome was taken. 



Subsequent examination showed these same forms to be present in the blood 

 of five other sheep, all of which were said to be cases of louping-ill. 



Examination of blood obtained in Tynemouth, from healthy sheep, failed to 

 discover any such form in it. 



The forms have not yet been sufficiently, under observation for the writer 

 to venture very definite opinions regarding them; but they are found free in the 

 blood plasma, apparently flagellates, and, very possibly, may be allied to the 

 trypansome in the tick. 



The author is aware that the small results as yet obtained by him prove 

 practically nothing, but he considers that they are enough to throw considerable 

 doubt on the present established theory as to the cause of louping-ill, and its 

 method of propagation. He recognises that the work of a thorough re-investi- 

 gation of the disease would require far more time and opportunities than are at 



