892 DISEASES CAUSED BY FTLTRARLE VIRUS 



The etiological factor which causes smallpox is still unknown. 

 Numerous researches aimed at the discovery of cultivatable micro- 

 organisms in the lesions or blood of infected patients have met with 

 uniform failure. Streptococci, though often found in the smallpox 

 vesicles and pustules, and often undoubtedly contributing materially 

 to the fatal outcome of the disease, may be regarded as purely 

 secondary in significance. 



Communications which have claimed the discovery of a protozoan 

 incitant of the disease have, on the other hand, been numerous and, 

 in some cases, have seemed plausible. Yet absolute proof has always 

 been lacking. The literature on this question is extensive and some 

 of the earlier contributions, such as those of Griinhagen, 2 of Van 

 der Loeff, 3 and of Pfeiffer, 4 possess historical interest only. The 

 work which, of recent years, has attracted the most serious attention 

 to this subject is that published by Guarnieri 5 in 1892. This observer 

 found, in the deeper cells of the epithelium covering the pustules, 

 both of smallpox lesions and of vaccination lesions, small bodies 

 which were easily stained by hematoxylin, safranin, or carmin. 

 Similar bodies could be observed in the cells of corneal lesions 

 experimentally produced in rabbits. Guaranieri claimed that he 

 distinguished both cytoplasm and nucleus in these bodies and 

 described both binary division and reproduction by sporulation as 

 in the sporozoa. He named the supposed protozoan ' ' Cy torryctes 

 variolae. " At about the same time Monti 6 described similar bodies 

 in the cells of the Malpighian layer of the skin covering smallpox 

 lesions and, a few years later, Clarke 7 confirmed the researches of 

 Guarnieri. Subsequently, many researches were carried out on the 

 same subject in this country, the most notable being those of Coun- 

 cilman, 8 Magrath and Brinckerhoff, and of Calkins. 9 The former 

 authors came to the conclusion that the bodies seen by Guarnieri 

 were parasites, and the latter author even described a distinct life- 

 cycle for these parasites comparable to that of some protozoa. 



2 Griinhagen, Arch. f. Dermat. u. Syph., 1892. 

 1 Van der Loeff, Monat. f. prakt. Dermat., iv. 

 *L. Pfeiffer, Zeit. f. Hyg., xxiii. 



5 Guarnieri, Arch, per le sc. med., xxvi, 1892 ; Cent, f . Bakt., I, xvi, 1894. 



6 Monti, Cent. f. Bakt., I, xvi. 



7 Clarice, Brit. Med. Jour., 2, 1894. 



8 Councilman, Magrath, and Brinclccrhoff, Jonr. Med. Res., xi, 1904. 



9 Calkins, Jour. Med. Res.,, xi, 1904. 



