384 EXPERIMENT STATION RECORD. [Vol.40 



continuation of those previously noted (E. S. R.. 37, p. 277), the results of 

 which have led t<> the conclusion that Ixodes ricinus transmits the infection. 



" The juice of certain edematous lymph glands and the blood from sheep 

 affected with louping-ill when inoculated into other sheep ran cause a disease 

 which may he fatal or may amount only to an indisposition. This disease 

 is characterized by high temperature, in some cases by coma, nervous tremblings 

 or twitchings, or even paralysis, by an absence of macroscopic lesions capable 

 of explaining the symptoms, ami by the presence of microscopic lesions in the 

 brain and cord of varying degree but referable to a pathological condition 

 describable as inyelo-encephalitis and similai to what are found in cases of 

 naturally contracted louping-ilL 



"Notwithstanding the first apparently negative results obtained with ticks 

 (1. ricinus) in various - which bail in a previous stage ted on sheep 



affected with louping-ill in the held [E. S. It.. .".7. p. L'77 1, it follows from the 

 later results obtained that larva- from females which as adults en - .in 

 affected sheep can give rise to a highly febrile and sometimes fatal disease in 

 other sheep, when put to teed upon them in very large numbers, and that 

 adults fed as nymphs on ;■ may have the same effect. It is pos- 



sible that the apparently negative results recorded in the first article an 

 owing to the circum that only a small proportion of ticks become 



carriers of infection, but it is a Is,, probable that negl< 'tin.: t,. take temperatoj 

 explains some of the apparently negative result 



"The blood and the juice of edematous lymph glands from cases arising 

 from experimental inoculation and from infestation by ticks can cause similar 

 symptoms and lesions when inoculated to other sheep in series. Ticks allow 

 to engorge on tin erimental cases during the reaction can. after molting 



to their next Stage, cause the disease in other sheep upon which they are put 

 to fc< d. 



••The Infective agent, whatever it is. can be transmitted from the female ticks 

 through the eggs to the next generation of larvae; but. although the positive 

 results SO Ear have been Obtained with larva- and adults, it does not follow 

 conclusively from the results available that the ticks in their nymphal si. 

 can not also transmit the diseai 



"Since the disease « ■: 1 1 1 he transmitted to sheep In series by inoculation, it 

 follows that the Infecting agenl i- not a toxin, but a living agent, capable of 

 reproducing itself to sonic extent in the tissues >( the animal into which it i~ 

 inoculated. It :ilso follows almost certainly from the fact of ticks transmitting 

 the infection that the int.. live agent is a protozoan parasite. Some of the 

 mononuclear leucocytes in edematous glands and in the Mood stream when 

 treated by Geimsa's stain show in their protoplasm chromatin bodies which 

 have some of the characteristics of protoz.au parasites. Including their stain- 

 ing reaction. It is not claimed, however, that a final statement can he made 

 that these chromatin bodies are parasites, and the causal agent of louping-ill. 

 Awaiting the results of further research on this special question, it is allowable 

 to summarize the evidence in favor of the parasite view being correct : i 1 I The 

 disease is tick-borne. (2) Inoculation with the Quids and organs of Bheep 

 containing the bodies reproduces the disease. (3) The bodies stain after 

 the manner of such parasites. (4) The causal agenl is apparently not ultra- 

 microscopic and the bodies are the only abnormal objects observable under 

 the microscope in materials Which convey the disease by inoculation, i .". i The 

 virulent material, if perfectly fresh, is sterile as regards bacteria (the infective 

 agenl appears to be retained by bacterial filters, which is evidence that it is 

 not ultramicroscopic). 



