172 PROTISTS AND DISEASE 



Spirochaetes in vaccinia. In the vaccine vesicle spiro- 

 chaetes have been found by Bonhoff, 1905. Many details 

 remain to be worked out, but enough has been established 

 to show that Cytoryctes guarnieri belongs to the same group 

 as Plassomyxa contagiosa. 



Intranuclear phases of Cytoryctes. In smallpox about 

 the same time Bosc in France and Councilman and others 

 in America described the intranuclear forms of the parasite, 

 the presence of which explains the difference between the 

 clinical courses of the two modifications of the disease : in 

 vaccinia the stages of Cytoryctes variolae are found only in 

 the cytoplasm of host-cells as in Fig. 49, 1 to 5 ; in smallpox 

 that stage also occurs and is repeated many times before 

 the distinguishing intranuclear generation appears, Fig. 49, 

 6 to 9. 



In 1904 Professor Calkins very kindly gave me some 

 sections of smallpox pustules stained by Borrel's indigo- 

 carmine picric acid method ; these sections show the intra- 

 nuclear stages to-day as clearly as when they were given to 

 me. Many of the minute subdivisions have left the nuclei 

 and are scattered in the sections. More observations on 

 fresh material are desirable to find out if they are the heads 

 of flagellates such as were described by Doehle in 1892. 



The first interpretation of the whole series of forms was 

 that Cytoryctes was a sporozoon ; later, after chromidia had 

 been generally recognised, Cytoryctes was thought to be a 

 Rhizopod ; finally after Dangeard's discovery of Nucleophaga 



