DISEASES PRODUCED BY ULTRA-MICROSCOPIC OUCJAMSMS 



This disease is known from Sweden, Germany, and the United 

 States. Flexner and Lewis, in 1909, have shown the organism to 

 be a filterable, probably ultramicroscopic, virus. The disea>e 

 may be transferred to the monkey. It probably spreads by inges- 

 tion of infected materials. 



Virus of Rabies 



Disease Produced. Rabies in animals. Hydrophobia in man. 

 Lyssa. 



The disease has been studied at great length by many in- 

 vestigators, and there is still great disparity of opinion as to the 

 nature of the cause. Remlinger and Riff at Bey, in 1903, showed 

 that the virus could be passed through a porous Berkefeld filter. 

 This has been substantiated since by several workers. As will 

 be seen below, this does not satisfactorily settle the problem, as 

 those who hold to the protozoan nature of certain bodies in the 

 nerve-centers in the disease, as they contend that extremely 

 minute plastic stages in the life-cycle of the organism might easily 

 pass through. 



Distribution. The disease is world wide in distribution. 



Nature of the Virus. Students of the etiology of this disease 

 may be divided into two groups those who believe in the presence 

 of a specific ultramicroscopic organism, and those who believe 

 in the presence of a protozoan with certain stages of development, 

 when the organism is small enough to pass the pores of the filter. 

 The latter theory has been developed by Negri. The organism has 

 been named Neuroryctes hydrophobia. In 1903 he demonstrated 

 the presence of specific bodies, which have been termed Xegri 

 bodies, in the larger ganglia-cells of the Ammon's horn, as well as 

 in other parts of the central nervous system. There is little ques- 

 tion but what these bodies are characteristic of the disease: the 

 disputed point is whether they are specific organisms or degenera- 

 tion products of the cell. Williams and Lowden summarize the 

 evidence of the protozoan nature of these organisms as follows : 



" They have definite characteristic morphology; this mor- 

 phology is constantly cyclic, i. e., certain forms always predominate 

 in certain stages of the disease, and a definite series of forms in- 

 dicating growth and multiplication can be demonstrated; the 



