THE PATHOGENIC RHIZOPODA 307 



vacuoles (Fig. 121), and sections of infected tissue not properly fixed 

 and stained give no satisfactory pictures of the organism, the place of 

 chromatoid granules and nuclei being taken by the vacuoles. Such 

 a picture is duplicated by improperly fixed parasites of dysentery 

 vacuoles appearing in the place of the formed parts of the cell. 

 These, again, are duplicated by the ordinary appearance of the 

 smallpox organism as it appears in sections of the skin (Fig. 123). 

 This structure has been, and is still, next to the so-called protozoan 

 inclusions in cancer, the most widely discredited cause of any malig- 

 nant contagious disease. The reason for the skepticism on the part of 

 pathologists generally is that the organism presents no appearance 

 that can be identified with the ordinarv cell, its lack of a vesicular 

 nucleus, its highly vacuolated appearance, and its development in 

 cells that are unquestionably pathological and degenerate, being, to 

 them, evidence against its protozoan or parasitic nature. 



While a great deal of the skepticism is due to traditional conserva- 

 tism on the part of medical men and disinclination on their part to 

 accept any but conclusively demonstrable evidence, it must be stated, 

 with all respect, that there is among them a strong tendency to ignore 

 such evidence as we do have in regard to the nature of these structures, 

 and disinclination to accept such evidence as similar to structures in 

 other protozoa. The difficulties attending the observations on the 

 organism of smallpox are aggravated by the fact that it is apparently 

 an exclusively human disease, and further, that the organism is an 

 intracellular parasite which quickly disintegrates upon leaving its 

 normal environment. One phase of the disease, however — vaccinia — 

 is suitable for experimental study, but at best this is but a mild disorder 

 when compared with variola inoculata of apes or with variola vera of 

 man. Until some means of studying it on an experimental basis is 

 established, we must make the best of the morphological evidence 

 jtfforded by imperfectly fixed tissues from human beings, or from 

 material in experimental animals with variola inoculata and vaccinia. 



The cell inclusions in the Malpighian layer of the skin were early 

 seen, interpreted as protozoa, and named Monocystis cpithelialis 

 by Pfeiffer, in 1887, but as he found so-called protozoa in all kinds of 

 diseased tissue, his observation did not create much comment nor 

 stimulate research. It was quite otherwise with Guarnieri, in 1892; 

 this skilful investigator inoculated the corneal cells of guinea-pigs and 

 rabbits with vaccine virus and w^th pustule contents, and found that 

 the peculiar cell inclusions cliaracteristic of smallpox and vaccinia 

 reappeared in each new epithelium inoculated. He found that the 

 structures appear with the greatest regularity in the vicinity of the 

 nucleus, the largest forms appearing around the point of inoculation, 

 while the most distant forms were the smallest. He regarded them as 

 protozoa, naming the form as observed in vaccinia, Cytorijcies vac- 



