328 



'SCIENCE. 



[N. S. Vol. XXII. No. 559. 



used a mixture of bile and blood from dead 

 animals before Koch's researches, and also 

 that Semmer in 1893 showed that serum 

 might be used for protective purposes ; but 

 still to Koch is due the credit of making 

 these processes practical. After he left 

 South Africa his work was continued by 

 Kolle and Turner, who greatly improved 

 the methods; and it is to them, and to the 

 other workers mentioned above, that we 

 owe the fact that rinderpest has now lost 

 its terrors. 



In the last recrudescence of this disease 

 in the Transvaal, in 1904, Mr. Stewart 

 Stockman, the principal veterinary surgeon, 

 and Dr. Theiler, thanks to the experience 

 and knowledge gained during the last ten 

 years, were enabled to stamp out the dis- 

 ease rapidly and completely. It is to them 

 also that we owe our knowledge of the 

 dangers of the intensive method of inocula- 

 tion, much used in the past and due to 

 Kolle and Turner, and the introduction of 

 the fighting against the plague by the in- 

 oculation of the healthy cattle by injections 

 of immune serum alone. 



In the tsetse-fly disease our advance in 

 knowledge has been in regard to the causa- 

 tion of the disease, and not in its preven- 

 tion; it is quite otherwise with rinderpest. 

 The contagium or cause of rinderpest is ab- 

 solutely unknown. "We know it exists in 

 the blood, nasal, mucous and other secre- 

 tions of the sick animal, as all these are 

 infective, but no one has seen it. The 

 smallest quantity of blood will give the dis- 

 ease if injected under the skin of a healthy 

 animal. We also know that the contagium 

 is not very resistant. Blood soon loses its 

 virulence after it leaves the body, and the 

 effect of drying or the addition of chemical 

 preservatives, such as glycerine, acts also 

 injuriously to the contagium, whatever it 

 may be. It evidently belongs to the ultra- 

 visible sort of micro-organisms, as it is said 

 to pass through a porcelain filter. 



How the contagium passes from the sick 

 to the healthy is assumed to be by contact. 

 No experiments have, as far as I am aware, 

 been made as to whether it is conveyed by 

 insects as well ; but, as Professor John Mac- 

 Fadyean says, as it spreads in all countries 

 and climates and seasons, and the con- 

 tagium is easily carried on the persons or 

 clothes of human beings, it is improbable 

 that insects have anything to do with it. 



It is in the methods of protective inocula- 

 tion that the great advance has been made 

 in our knowledge of this disease. Ten years 

 ago no means were available to stay the 

 progress of this plague; now it has lost its 

 terrors. As soon as it appears it can be 

 immediately attacked and stamped out. 

 This is done by rendering the surrounding 

 cattle immune to the disease by injecting 

 immune serum. This serum is prepared by 

 taking immune cattle and hyper-immuniz- 

 ing them by the injection of large quanti- 

 ties of virulent blood, so as to make their 

 blood serum as anti-toxic as possible. If 

 there are no immune cattle at hand, cattle 

 can be immunized by Koch's bile injection 

 method and then hyper-immunized ; but, of 

 course, in practise — for example, here in 

 the Transvaal — large quantities of immune 

 serum are kept ready for emergencies, and 

 a herd of immune cattle kept up for the 

 supply of the serum. This satisfactory 

 state of affairs, as far as this disease is con- 

 cerned, is, of course, the outcome of an 

 immense amount of thought and experi- 

 ment, and I have already mentioned the 

 chief scientific men to whom this country 

 owes this great boon. 



Different methods of immunizing have 

 been tried during these years. Up to 1903 

 the prevailing custom was to use what was 

 known as the virulent-blood and serum 

 method. That is to say, immune serum 

 and virulent blood were injected at the 

 same time, in order that the animal might 

 pass through a modified attack of the dis- 



