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Scientific Memoirs by
peculiarity of the present case rests on the conjunction of phenomena pre-
sented rather than upon any single phenomenon, and therefore it may be
most convenient to consider separately the pathological state involved and
the organism concerned. As regards morbid symptoms, whilst in the horse
and mule these become so marked, they are described as being very insiduous
at their beginning and liable to apparently complete intermissions. Animals at
work have been found to present a highly contaminated state of the blood ;
others have died suddenly or unexpectedly, and there are some natural variations
of symptoms in different provinces and between the horse and mule. These
facts are mentioned here with reference to the likely detection, or non-detection,
of morbid signs in animals not domesticated and only casually inspected : even
in the rat at Bombay, it was not clear to me that infected animals did not at
some time and in some manner or degree suffer from their blood-contamination,
the probability being that they did so suffer ; and as regards the few instances
reported of deer, frogs, and fishes in whose blood protozoa have been detected
without the remark being made of illness associated therewith, this datum, too,
is a negative one and similarly open to uncertainty. I think also that the
" surra " data respecting inoculated dogs raise the question whether these
animals may not sometimes suffer,—Mr. Steel's experiment pointing to the
affirmative, and that with the monkey being likewise noteworthy as a varia-
tion from the parent type : and, briefly, there appears to me some indication
that, morbid signs amongst the different species of animals being likely to
differ, there will eventually be elicited a' transitional series of such phenomena
concurrent with one and the same monad blood-contamination, beginning with
the mildest, e.g., in rat or some dogs and ending with severest, e.g., in equines.
Such inference would be supported by analogy with the anthrax infection,
concerning which it is said that there is nothing fixed or absolute in the
receptivity or the immunity of any one species, and that variations occur amongst
even individuals of the same species (Straus. l.c. douzième leçon) : thus, rats
Prove to be only exceptionally inoculable, and sheep of Algerian race are natur-
ally almost Wholly immune to anthrax, analogous to which fact is the asserted
non-liability to " surra" of the ass, whilst the horse and the hybrid mule are both
highly susceptible. The present :topic might be further illustrated, but it will
suffice if a fairly reasonable explanation of some difficulties be already apparent.
Perhaps the greatest difficulty, however, yet remains, that, namely, which re-
quires for its solution either the assumption that the hæmatozoon in question
has per se no essential connection with the symptoms of " surra," being only an
attendant or quasi-incidental phenomenon (a) , or else the admission that the
hæmatozoon may retain its morphological aspect and capacity of life whilst
parting with all or most of its virulent biological properties (b). Regarding,
first, the relationship of organism to morbidity, nothing new has yet been elicited