History, Prevalence, Etiology. 425 



an organism similar to the human diphtheria organism. But these 

 and other similar findings influenced but" slightly the view that bird 

 diphtheria is a baeillary infectious disease, and were explained by the 

 assumption that various bacteria participate in different eases in the 

 diphtheritic diseased processes, a view which indicated a degree of un- 

 certainty as to any positive knowledge in this regard. 



The etiology of chicken pox was elucidated acceptably when Marx 

 and Sticker (1902) brought proof that the pock virus will pass through 

 a porcelain filter and therefore belongs to the filterable infectious sub- 

 stances. This has since been confirmed by Juliusberg, Borrel, Loewen- 

 thal, Burnet and others. 



Experiments following this discovery have led to results which 

 completely shattered the existing view that the etiological factor of 

 the two diseases differed. It is true that Eoell (1867) suspected that 

 the changes in the oral mucosa and skin were due to the same causative 

 agent, and this view is also expressed in the work of Rivolta & Delprato 

 (1880) as well as Pfeiffer (1889) and Kinsley (1907). Moreover 

 from a practical point of view, considering the difficulty in differential 

 diagnosis, this did not seem unlikely, but experimental support was 

 not obtained until Carnwath (1908) succeeded in producing a diph- 

 theritic disease of the mucous membranes from pure pox material, and 

 with diphtheritic material produced chicken pox. These experimental 

 results, doubted by Bordet & Fally and also by Jowett, were confirmed 

 by Schmid, Uhlenhuth & Manteufel, and also by Ratz, and further 

 experiments directed towards the solution of some contested details 

 such as virulence of the blood in pure diphtheria, role of the bacteria 

 present in the pseudo-membranes, etc., will no doubt soon establish the 

 etiological identity of the two forms of disease definitely. 



Prevalence. Both forms of disease occur particularly in 

 fowls (chickens, turkeys, pheasants, peacocks), also in pigeons, 

 and much less commonly in water fowls. In the southern 

 regions (Italy, Tunis) the diphtheritic form rages with greater 

 virulence and sometimes presents a septicemic character, but 

 in northern regions the losses, especially in pedigreed fowl 

 farms, are heavy on account of the frequent severe invasion 

 of the disease and high mortality. 



Etiology. The experiments of Marx & Sticker have shown 

 that the fluid obtained by maceration of epithelial nodules in 

 physiological salt solution is infectious after passing through 

 a Berkefeld filter, since after the inoculation of the filtrate into 

 the skin of chickens the characteristic epithelioma developed, 

 which could be inoculated from one animal to another. 



Borrel, Lipschiitz, as well as Prowazek, are inclined to consider as etiological 

 agents, very minute, hardly 0.25 /i sized, sjjherical or biseuitform organisms, 

 found in large quantities in virus-emulsions, and which can be demonstrated by 

 Giemsa's as well as by LoeflBer's flagellum stain. By penetrating into cells they 

 may cause the development of the frequently mentioned "inclusions" in the epi- 

 thelial cells, as products of reaction. Prowazek named them, as well as similar 

 formations in vaccinia, rabies, etc., Chlamydozoa, since they caused vacuoloid reac- 

 tion products in the infected cells. 



Tenacity. The pox virus is rather resistant to external influences. Enclosed in 

 epithelial masses it is not destroyed by complete drying or exposure to diffuse day- 

 light for several weeks; heating to 60°C. for three hours, cooling to minus 12''C. for 



