So6 APPENDIX A. 



Protozoa as Causative Agents. — Van der Loeff and L. Pfeiffer early 

 drew attention to the presence of small amoeboid bodies in the blood 

 and epithelial cells of the skin and mucous membranes of persons affected 

 with smallpox, which they believed to be the cause of the disease, and 

 considered them as protozoa. Later, Guarnieri, in a series of studies 

 upon rabbits which he had inoculated in the cornea with active vaccine 

 lymph, described bodies occurring in the lesions similar to those of Van 

 der Loeff and Pfeiffer. He further showed that when using naturally 

 inactive lymph, or filtered vaccine lymph, no bodies were produced in 

 the corneal cells, but they again appeared if the material held back by 

 the filter were inoculated. 



Ruffer and Plimmer describe as occurring in clear vacuoles in the 

 cells of the rete Malpighii at the edge of the pustule, in paraffin sections 

 of vaccine and smallpox pustules carefully hardened in alcohol, and 

 stained by the Ehrlich-Biondi mixture, small round bodies about four 

 times the size of a staphylococcus pyogenes, coloured red by the acid 

 fuchsin, sometimes with a central part stained by the methyl-green. 

 These appear to multiply by simple division, and in the living condition 

 exhibit amoeboid movement. Similar bodies have been described by 

 Reed in the blood of smallpox patients and of vaccinated children and 

 of calves. > 



In an exhaustive research von Wasielewski, upon a larger scale repeating Guar- 

 nieri's work, largely confirms the latter's observations. He utilised both human and 

 calf vaccine lymphs, and in one series, using bacteria-free calf lymph, he was able to 

 reproduce the peculiar bodies in the cornea of a rabbit with the forty-eighth transfer, 

 passing from one rabbit to another throughout the series. He found similar bodies 

 in the epithelial cells in a case of smallpox, too. His conclusions are that these 

 bodies are neither cell-inclusions of leucocytic origin, nor degeneration products of 

 the epithelial cells themselves, but, with Guarnieri, believes that in all probability 

 they are the causative factors of the disease. 



Another observer, Gorini, lays great stress upon the presence of coccus-like bodies 

 free and in the cells of vaccine vesicles and in the lymph, which occur singly, in pairs, 

 and in tetrads. He thinks that possibly their nature is bacterial, and that, being 

 absent in inactive lymph and in the cells of ordinary inflammatory origin, they 

 possibly may be the cause of the phenomena of vaccination. Gorini believes that the 

 bodies described by Guarnieri and von Wasielewski {cytoryctes vaccinte) are simply 

 the products of cell degeneration. 



In the presence of such interesting but divergent findings, it is plain 

 that more precise research of a confirmatory nature is required before 

 any of these bodies can be accepted as being the cause of smallpox or 

 vaccination. 



The Nature of Vaccination. — As we are ignorant of the cause of small- 

 pox, we can only conjecture what the nature of vaccination is. From 

 what we know of other like processes, however, we have some ground 



