546 REPORT—1905. 
from the effect of the inoculation, he states to be about 5 per cent. It is higher in 
horses, but he expects shortly to attain the same result in them. During the last 
Horse-sickness season he exposed 200 immunised mules to natural infection in 
various parts of the country. Of that number only one died with symptoms of 
Horse-sickness. As Dr. Theiler is himself communicating his method in detail to 
the Association, I need not enter more fully into it. 
The man who discovers a practical method of dealing with Horse-sickness 
will be one of the greatest benefactors of this country. There has always been a 
tradition that a large money reward is awaiting this discovery. I do not know 
whether this is well founded or not, but certainly such a work would well deserve 
the highest possible reward. The best reward is to give the successful investigator 
more opportunity and more assistance in pursuing his beneficent work. The 
reward given by the French people to Pasteur was the Pasteur Institute; by the 
German Government to Koch, the Imperial Hygienic Institution. 
Catarrhal Fever of Sheep: Blue Tongue. 
This disease was first described by Hutcheon, the Chief Veterinary Surgeon of 
Cape Colony.! It is very similar in many respects to Horse-sickness. Both these 
diseases occur most often in low-lying, damp situations, such as river valleys and 
the coast plain. ‘They also occur at the same time of the year; that is, from 
January to April. Blue Tongue, like Horse-sickness, is probably carried from the 
sick to the healthy by means of some night-feeding insect. At the same time the 
diseases are not identical, since the inoculation of Horse-sickness blood into a sheep 
does not give rise to Blue Tongue, nor the blood of the sheep injected into the horse 
give rise to Horse-sickness. 
‘To Mr. Spreuill, Government Veterinary Surgeon in Cape Colony, acting under 
the advice of Hutcheon, is due the credit of proving that a preventive serum could 
be prepared capable of immunising sheep against this disease. Dr. Theiler informs 
me he has repeated Mr. Spreuill’s experiments, and they hope to introduce this 
method of inoculation at an early date. 
Heart-water of Cattle, Goats, and Sheep. 
This disease was also first clearly described by Mr. Hutcheon. It occurs in 
the Transvaal, Natal, and Cape Colony, and is responsible for much of the yearly 
loss among the cattle, sheep, and goats. 
Like the last disease—-Blue Tongue—it resembles Horse-sickness in many ways, 
and, in fact, has been described by Dr. Edington as being identical with it. Like 
Horse-sickness, it is a blood disease with an invisible parasite, so that blood 
injected under the skin of susceptible avimals gives rise to the disease. One 
difference between the parasites of the two diseases is, that whereas that of Horse- 
sickness is contained in the fluid of the blood, that of Heart-water is probably 
restricted to the red blood-corpuscles. The serum separated from the blood is 
incapable of giving rise to the disease, and the straw-coloured pericardial fluid, when 
injected into susceptible animals, fails to give rise to any symptoms of the disease. 
Horse-sickness blood filtered through a porcelain filter is still infective ; the opposite 
holds good up to the present with Heart-water. Horse-sickness blood can be kept 
for years without losing its virulence; Heart-water blood loses it in forty-eight 
hours. 
Heart-water has a peculiar distribution, being restricted to the certain tracts 
of country with a warm, moist climate. It is known to farmers that if they 
remove their flocks to the high veld the disease dies out. 
To Lounsbury is due the credit of explaining these facts. He found that the 
disease is carried from sick to healthy animals by means of the bont tick, 
3 It is to Mr. Hutcheon that South Africa owes its knowledge of many stock 
diseases. For the last twenty-five years he has laboured with the utmost earnestness 
in Cape Colony, often under trying conditions, and his description of the various 
diseases formed the basis of all the modern work done on the subject. 
