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TEE AGRICULTURAL JOURNAL. 



although it may happen that, in extremely 

 bad seasons, the scourge may make its 

 appearance even there. The disease oc- 

 curs as an epidemic only at certain periods 

 of the year, but occasional cases may also 

 be seen the whole year through in a bad 

 District. The horsesickness season for the 

 Transvaal are the months from January 

 until May ; especially the three months, 

 February, March, and April. Bad years 

 change with good years. The former 

 ones have again a certain conformity, and 

 are characterised by much rain in the 

 beginning of the year, followed by ex- 

 treme warmth. Again, when all circum- 

 stances for the development of the disease 

 are present, certain conditions are wanted 

 to infect a horse. These circumstances 

 are very much discussed, yet the practical 

 outcome is, to keep horses stabled and not 

 to let them go out before sunrise and after 

 sunset. Stabling does, to a very large 

 extent, give immunity against the disease, 

 though it may often fail. Within an un- 

 healthy district there are still spots and 

 places known to be more dangerous than 

 others, namely, near rivers and marsh 

 lands. The disease disappears more or 

 less of a sudden with the first frosts. 



The farmers know two forms of horse- 

 sickness, which classification is sufficient 

 for the purpose. These forms are dunkop 

 and dikkop. They are only different 

 forms of one and the same cause ; the 

 first one bearing especially on the lungs, 

 the eecond one at the heart, the swollen 

 head being only a secondary symptom. 

 We always can produce, artificially, horse- 

 sickness with blood or any other morbid 

 matter of a diseased horse by subcutaneous 

 injection. One and the same virus 

 may produce, in one instance, the " dun- 

 kop," and in another instance the " dik- 

 kop." Out of many experiments, I came 

 to the conclusion that the different forms 

 of horsesickness are only the result of the 

 different resistance of the animal tissue. 

 Horsesickness may run so rapidly that 

 death follows apoplectically ; or distinct 

 lung troubles are present for a certain 

 time ; or swellings appear on the head, 

 and the animal l)ecomes very weak. In 

 the first case the poison, produced by the 

 pathogenic micro-organism, attacks the 

 whole system from the very start, and 

 does not come to i)ronounced sym})toms ; 

 in the second instance the lungs are the 



weaker organs, and in case these are 

 strong enough to stand the attack, then 

 the heart fails. The effusive swellings 

 are very likely the result of the altered 

 blood-vessels, which let part of the blooel 

 aransudate. Following this line of de- 

 velopment, we understand that dikkop 

 lasts, as a rule, longer than dunkop, and 

 and that dikkop, so to say, never will end 

 with dunkop, bat vice versa dunkop 

 either ends as such, or with dikkop. Of 

 course mixed forms may appear where 

 the symptoms of dun and dikkop are 

 present at the same time. 



I said that blood and any morbid matter 

 of a horsesickness horse are virulent, and 

 invariably produce the disease in a sus- 

 ceptible horse. The incubation time 

 varies very much. As a rule eight to 

 twelve days after infection the first 

 symptoms may appear, but very often I 

 have seen them coming only from the 

 fifteenth to the twenty-fifth day, and even 

 as late as on the thirty-fifth day. 



This will explain how difficult it is to 

 mark the time when a certain horse did 

 become infected. Although the blood of 

 a sick horse is invariably virulent, there 

 is no possibility whatever of demon- 

 strating the micro-organisms, either by 

 microscope or by culture. They are so 

 small that they pass through a Chamber- 

 land's porcelain filter, where no visible 

 microbe passes. As Mr. Macfadean, of 

 London, points out, it is not likely that, 

 for such a small thing, a sufficiently 

 magnifying power ever will be con- 

 stritcted. 



The following facts are borne out by ex- 

 periments : — 



Horsesickness blood keeps its virulency 

 for at least fourteen months, when in 

 liquid state, but loses it when dried. As 

 little as twelve hours in the shade is 

 sufficient to kill the micro-organism when 

 the l)lood is dry. The virulency is not 

 suspended when the blood becomes quite 

 putrefactive. Virulent blood, kept for 

 many months in ice, does not lose its 

 infective power when liquid. It is pos- 

 sible to produce the disease with as little 

 virulent blood as one-thousandth part of 

 one com. by subcutaneous injection, 

 although the individual disposition and 

 resistance of a horse can vary very much 



