Immunization. 55 



IV. Protective vaccination with thread covered with spores. 

 (Method of Thomas.) Thomas, a veterinary surgeon at 

 Verdun, recommends a spore-containing vaccine, the prepara- 

 tion of which is not given (supposedly through growth in frog's 

 bodies) ; with this vaccine silk threads (fils virulents, black- 

 legine) are impregnated which he introduces into the sub- 

 cutaneous tissue of the tail. In his opinion, this method is 

 more effective than the original Lyons method, because a 

 blackleg culture develops around the threads left under the 

 skin which exerts a continued immunizing action on the 

 organism (in an experiment with sheep, he found virulent 

 spores and bacilli between the silk threads 328 days after the 

 vaccination). 



The vaccination instrument consists in a trocar fastened to a handle of wood 

 behind the tip of which is a cut for placing the silk threads. One dose of the 

 vaccine consists of 7 to 8 short threads which are fastened together at the ends 

 by means of a metal nipper. At the vaccination, after the threads have been placed 

 in the notch and the nipper is cut away, the needle is stuck deep into the sub- 

 cutaneous tissue near the end of the tail (in calves behind the shoulder) as nearly 

 as possible parallel with the surface of the skin, and immediately pulled out again, 

 whereby the threads slip off from the needle and remain in the depth of the vac- 

 cination canal. The vaccination is either performed twice with a weaker and a 

 stronger vaccine, or only once with the latter. 



In America 135,000 head of cattle were vaccinated in the years 1899 and 1900 

 according to this method (one single vaccination). According to the reports of 

 the results, the vaccination itself caused no losses, while later, as a result of natural 

 infection, 0.4 to 0.7% of the vaccinated animals died. 



Lately this method has also been used in Germany, and Warringholz obtained 

 good results in 406 and Witt in 700 animals; on the other hand, in Alsace-Loraine 

 (1901) 22 vaccinated animals out of 260 died, while in Hungary, Viasz lost 16 out of 

 70 vaccinated animals within 3 weeks. 



According to investigations by Eegn, the vaccine is very impure and con- 

 tains particularly a large number of staphylococci ; in connection herewith, Guillebeau 

 frequently observed vaccination abscesses among cattle in the canton of Berne. 



V. Other methods of immunization. It is also possible to 

 immunize cattle by means of other methods, which, however, are 

 little used in practice, and only deserve attention from a scien- 

 tific point of view. 



1, Protective vaccination with non-attenuated virus. Cattle 

 may be immunized by subcutaneous injection of a small amount of 

 the juice from the swellings into parts of the body with low tem- 

 perature and dense subcutaneous tissue. The subcutaneous injection of 

 1 to 6 drops into the end of the tail causes neither local nor general 

 symptoms; 10 to 15 drops will cause an increase in temperature of 

 1.5°C., while 20 drops will cause a local swelling. The further away 

 from the trunk the injection is made the milder the symptoms appear; 

 injections in the vicinity of the root of the tail, however, often cause 

 severe disease. 



According to Arloing, the direct intravenous injection, although 

 it requires more manual skill, is the most favorable. It consists in 

 injecting 3 to 4 drops of the serous fluid of a swelling into a vein of 

 the animal, care being taken that none of the liquid gets into the peri- 

 vascular connective tissue. After a regularly performed vaccination, 

 general symptoms, such as a slight elevation of temperature and loss of 

 appetite, will appear, after the disappearance of 7.'hich tiis animal 



