388 RABIES 
“The Negri bodies as shown by the smears as well as by the section 
are specific to hydrophobia. 
“Numerous ‘bodies’ are found in fixed virus. 
“**Bodies’ are found before the beginning of visible symptoms—.e., 
on the fourth day in fixed virus, on the seventh day in street virus, 
and evidence is given that they may be found early enough to account 
for the appearance of infectivity in the host tissues. 
“Forms similar in structure and staining qualities to the others, but 
just within the limits of visible structure at (1,500 diam. magnifica- 
tion) have been seen. Such tiny forms, considering the evidence they 
give of plasticity, might be able to pass the coarser Berkefeld filters. 
“The Negri bodies are organisms belonging to the class Protozoa. 
The reasons for this conclusion are: (a) They have a definite, 
characteristic morphology; (b) This morphology is constantly cyclic, 
i. e., certain forms always predominate in certain stages of the disease, 
and a definite series of forms indicating growth and multiplication can 
be demonstrated; (c) The structure and staining qualities, as shown 
especially by the smear method of examination, resemble that of 
certain known Protozoa, notably of those belonging to the sub-order 
Microsporidia.” 
The proof that the “‘Negri bodies” are living organisms is sufficient 
proof that they are the cause of hydrophobia; a single variety of living 
organisms found in such large numbers in every case of a disease, and 
only in that disease, appearing at the time the host tissue becomes 
infected in regions that are infective, and increasing in these infective 
areas with the course of the disease, can be no other, according to our 
present views, than the cause of that disease. 
The Negri bodies or cell inclusions vary in shape. The most com- 
mon forms are round or oval. The round bodies are from 0.5 to 23u. 
in diameter, while the oblong ones vary from 0.5 to 1.5 to 5 to 27M. 
The round or oval forms are by far the most common. Irregular 
forms are occasionally seen. In preparations stained with eosin and 
methylene blue they appear as bright red bodies containing one or two 
nuclear-like structures which are surrounded by anumber of other 
small circular, regular bodies. They are said to preserve their form 
even when the brain tissue has undergone marked degenerative 
changes, after prolonged immersion in glycerin and after several days’ 
drying. A number of workers report finding them quite uniformly. 
Schiider does not consider them as the cause, largely because his virus 
passed through a filter that retained the cholera spirillum. 
