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they are forms which differ from those either after death in the 
normal tissues or liquids of the body, or during life in the products 
of primary or secondary inflammation, The diseases in which 
such forms have been discovered are small-pox, sheep-pox, a peculiar 
disease of horses and cattle known as splenic fever, relapsing 
fever, and lastly enteric fever. I take as examples the two diseases 
investigated by Dr. Klein with such brilhant success—sheep-pox 
and enteric fever. The former disease does not occur in man, 
not being communicable to him, but it has a very close resem- 
blance to ordinary small-pox, a resemblance so close that we must 
believe the pathogeny of the two to be the same. 
Dr. Philpot illustrated, by diagrams enlarged from the drawing 
of Dr. Klein, the various structures discovered by that observer in the 
lymph taken from the vesicles, and pointed out the highly 
refractive spheroid regarded by Dr. Klein as the only form charac- 
teristic of the lymph of sheep-pox in its aetive condition. 
When the sheep is innoculated with the lymph in addition to 
ordinary anatomical changes occurring at the seat of innoculation 
in the development of the primary pock, Dr. Klein observed 
changes connected with the growth and reproduction of the 
micrococci. The lymphatic vessels in connection with the pock 
become distended with a matter which resembles coagulated plasma. 
In this, organised bodies appeared which neither belonged to the 
tissue, nor are referable to anatomical type, viz., spheroid or ovoid 
bodies, having the characters of micrococci and branched filaments. 
The process thus commenced makes rapid progress. After one or 
two days the greater number of lymphatics of the affected parts 
of the corium become filled with the vegetation above described ; 
and on careful examination of the masses it is seen that they 
present the character of a mycelium from which necklace-like 
terminal filaments spring, each of which breaks off at its free end 
into condia. In most of the filaments a jointed structure can be 
made out. When the vesicles have formed they are seen to 
contain masses of vegetation similar to those found in the 
lymphatics, with this difference, filaments of which the masses are 
composed are of such extreme tenuity and the conidia are so 
small and numerous, that the whole possesses the character of 
zoogloea rather than of mycelium. Similar changes take place in 
the secondary pustules. 
In the case of enteric fever, experienced pathologists had 
already argued thatit was a disease due to a specific poison, that 
the contagium is a specific and living organism, which, when 
transmitted from a diseased to a healthy individual, produces the 
same disease in the latter; and further, that the chief if not the 
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