Investigations into the Nature, Causation, and Prevention of Texas or Southern Cattle Fever Page: 65
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THE CAUSATION OR ETIOLOGY OF TEXAS FEVER.
been observed. The only other organs in which free bodies are found
are the kidneys. (Plate vI, Fig. 3, and notes on Nos. 47, 50, 66, 69, 74,
95, 128, 134, 139.) These organs are generally filled with infected cor-
puscles. In the fever stage we may find in dried films and in stained
sections very few corpuscles which do not contain a pair of parasites.
When the number of corpuscles has fallen quite low before death and
the destruction has practically ceased there may still be found, in dried
and stained films of the parenchyma, immense numbers of free para-
sites. They appear as roundish coccus-like bodies grouped in pairs
and varying slightly in size, never as pyriform or fusiform bodies. To
a casual observer they might appear as coarse granulations of broken-
down cells and cell nuclei, but a little study and comparison of different
cases soon dispels this view.
THE MICROORGANISM IN THE MILD TYPE OF TEXAS FEVER.
We have thus far considered only those forms of the parasite found
in the acute type of the fever. This type will now be understood to
be one in which there is a very rapid multiplication of the micro-para-
site in the blood vessels corresponding to an equally rapid disappear-
ance of the red corpuscles. The forms of the micro-parasite are pyri-
form and fusiform bodies chiefly intraglobular, occasionally free. The
post-mortem forms are roundish. In size the pyriform bodies are quite
large, and the question arises: are there any smaller forms to be found ?
For these we must turn to the mild (usually autumnal) cases of the
disease. It is an interesting fact that these cases are characterized by
the presence of the smaller stages of the parasite. While the pyriform
bodies are not entirely absent they are very rare. In the acute type
only the latter and not the former are seen.
In the mild type (see p. 22) we have from 5 to 50 per cent of the red
corpuscles in the circulating blood infected for a period of from one to
five weeks. In the acute type, on the other hand, the circulating blood
contains usually from one-half to 2 per cent of infected corpuscles; 10 to
15 per cent is a rare occurrence, usually just before death. In the fresh
preparations of blood this small stage of the parasite is as a rule invis-
ible. Rarely we may observe it on the very border of the corpuscle as a
round pale spot about 0.5 1 in diameter, which does not change its place.
When dried films of blood are stained in alkaline methylene blue the
parasites appear as round coccus-like bodies from 0.2 to 0.5 ~ in diameter
and situated within the corpuscle on its border. They sometimes
appear as if situated on the border but outside of the corpuscle.
As a rule only one is found in a corpuscle. (Plate IV, Fig. 1, 2, 3.) In
many cases a division of the coccus-like body into two, could be clearly
made out. The separation was noticeable as a paler line anld a con-
striction at either end similar to the division of certain micrococci.
This division usually appeared in all bodies of a preparation from one
10320---No, 1 -565
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Smith, Theobold & Kilborne, Fred Lucius. Investigations into the Nature, Causation, and Prevention of Texas or Southern Cattle Fever, book, 1893; Washington D.C.. (https://texashistory.unt.edu/ark:/67531/metapth143538/m1/65/: accessed April 26, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu; crediting University of Texas Health Science Center Libraries.