302 Sheep Pox. 



mutual relationship of these forms of the disease. On the con- 

 trary, the uniformity of the development of the specific patho- 

 logical processes points to the probability that the pox disease 

 was originally a specific, independent affectiou of one of the 

 susceptible species of animals or of man, and was here and 

 there transmitted to other species of animals. However as 

 the virus, in the course of time, passed through many genera- 

 tions of various species of animals it adapted itself in point of 

 virulence, and probably also in its other properties, to the 

 organisms of these respective species of animals. As the result 

 of this the pathogenicity of such an adapted virus has been 

 partly or entirely lost against other species of animals. 



Literature. Jenner, Inqu. into the causes u. effects of the Variolae- Vaccinae. 

 London 1798.— Chauveau, Eec, 1866, 305 u. 625; Bull., 1893, 51. — Bouley, Diet, 

 de m^d. v6t.,' 1871, IX, 451.— EolofC, Pr. Mt., 1870-71.— Bollinger, Volkmanns 

 Samml. klin. Vortr., 1877, Nr. 116 (Lit.).— DieckerhofC & Grawitz, V. A., 1885, 

 CII, 148.— Prowazek, Arb. d. G.-A., 1905, XXIII, 535.— Miihlens & Hartmann, 

 Zbl. f. Bakt., 1906, XLI, 41 (Lit. on the so called vaccine-virus).- Voigt, Z. f. 

 Infkrkh.. 1909, VI, 101.— Siiple, A. f. Hyg., 1908, LXVIII, 237. 



(a) Sheep Pox. Variola ovina. 



{Scabrot, Schafpocken [German]; Clavelee, PicoUe [French]; 

 Vajuolo pecorino [Italian].) 



History. Sheep pox was probably introduced from Central Asia, 

 since human pox which is closely related to pox of animals is known 

 to have existed in India a long time before the birth of Christ. Sheep 

 pox was extensively studied for the first time by Joubert and Rabelais 

 towards the end of the sixteenth century; its infectiousness however 

 was established by Bourgelat in 1763. As a result of the customary 

 immunizations of sheep at that time, and through the use of Spanish 

 sheep for the improvement of existing breeds, the disease attained a 

 large distribution in Europe. 



The etiology and pathogenesis of the disease were investigated 

 especially by Chauveau (1868) in more recent times by Borrel (1902), 

 whose work has created great interest in the matter of immunization, 

 which had been neglected for a time. 



Occurrence. Pox among sheep has in recent times been 

 entirely eradicated in the northern and central countries of 

 Europe by proper measures, while in France and in the 

 countries lying south and east the disease occurs even now in 

 an epizootic form. In the affected territories extensive out- 

 breaks appear especially during the warm weather, but even 

 in these localities the disease does not attain the extension of 

 former times. Its economic importance results from the great 

 losses which occur occasionally, and also from the considerable 

 loss of wool which follows the disease. 



Severe outbreaks are mentioned as having occurred in the be- 

 ginning of the last century, thus Salmuth estimated in 1804 that the 



