THE INFECTIOUS DISEASES. 275 



THE EXCITANT OF SMALLPOX. 



Bacteria. The large number of studies which have been made of the 

 skin lesions of smallpox and of vaccine lymph have shown that bacteria 

 of various kinds are frequently present. 1 Streptococci and staphylococci 

 are especially common in the pustules and may be present in the blood 

 in later stages of severe or fatal cases. 2 It is probable that the pyogenic 

 cocci are of great importance as complicating factors in the disease. 

 But there is no evidence at hand that these or any other bacteria are its 

 primary excitants. 



Protozoa. While it was natural that the most painstaking search 

 should be made for bacteria in the lesions of smallpox, there have been 

 from the first many obvious reasons for the conjecture that this disease 

 as well as the other exanthemata might be incited by organisms of a 

 different nature. In fact, as early as 1886 and 1887 bodies were found 

 in the pustules by Van der Loeff and L. Pfeiffer, which they conjectured 

 to be protozoa. It was not until 1892, however, when Guarnieri under- 

 took a series of noteworthy experiments in animals, that the nature of 

 the suspected structures in vaccine lymph became clearer. Guarnieri 

 inoculated vaccine lymph into the cornea of rabbits and noted the ap- 

 pearance after a few days in increasing numbers in the epithelial cells 

 of the structures which had been previously discovered in the contents 

 of smallpox pustules. In some of these bodies he believed that he saw 

 amoeboid movements. These bodies, which were called " vaccine bodies, " 

 he regarded as protozoa and named the species Cytoryctes vacdnce. 3 



These observations of Guarnieri on the vaccine bodies found in the 

 lesions of both vaccinia and variola were confirmed by Wasielewski * and 

 many other observers. 



The vaccine bodies of Guarnieri are spheroidal, oval, or irregular 

 structures from one micron to four or even eight microns in diameter, 

 staining readily with various dyes, the central portion giving in general 

 the staining characters of nuclear substance, a peripheral zone being 

 sometimes differentiated by cytoplasmic stains. The bodies often lie 

 close upon the border of the nucleus of the epithelial cells, sometimes 

 lying in a depression of the nuclear border. They may, however, lie in 



of the absolutely identified and well-known germ which induces the disease. On the 

 other hand, it is not a little curious that in smallpox and in hydrophobia effective meth- 

 ods of immunization should have been perfected without precise knowledge of the 

 micro-organisms which incite the diseases, and yet by procedures which though some- 

 what empirically hit upon, are nevertheless in close accord with those which the most 

 recent studies on immunity in general have shown to be effective. Thus in both small- 

 pox and hydrophobia the material used for protective inoculation is that which has 

 been artificially reduced in virulence; in the one case smallpox by its passage 

 through the body of a relatively insusceptible animal; in the other hyd'rophobia by 

 drying in the air. 



1 See Huguenin, Lubarsch and Ostertag's " Ergebnisse, " Jahrg. iv., p. 387, bibl. 



2 See report by Eicing, Trans. Assn. Am. Phys., vol. xvii., 1902, p. 213; also Perkins 

 and Fay, Jour. Med. Res., vol. x., 1903, p. 180. 



3 This name was given because the bodies frequently lay in small spaces in the cell 

 protoplasm, which he assumed to have been formed by the destructive action of the 

 parasite. 



4 Consult, for a most admirable summary of the subject with original studies, pho- 

 tographs, and bibliography, Wasielewski, Zeitsch. f. Hygiene, Bd. xxxviii., 1901, p. 212. 



