MICROSCOPIC ORGANISMS IN INTESTINAL CANAL, 283 
sporangia being apparently indefinitely produced so long as the 
spore-cells obtain access to the medium while in a recent state, 
if certain conditions of temperature and moisture be provided. 
Further, we have ascertained that the reproductive elements are 
capable of retaining their vitality for prolonged periods when in 
a dry state, and that they are then also capable of resisting 
influences which are fatal to them in activity, so that a constant 
supply is always at hand for introduction. These may of 
course obtain access to the body by various means. The 
transfer in the case of cattle probably occurs by means of 
fodder in which the sporangia are constantly liable to be 
present. In the case of the human subject it, no doubt, occurs 
in various ways, the great means of diffusion in all probability 
being the air. That the air is the chief agent by which the 
reproductive elements are diffused appears probable for several 
reasons. ‘There can be no doubt as to the constant entrance 
of the reproductive bodies into the air, both as isolated spores 
and entire sporangia. The sporangia, when thoroughly dried 
are detached by the slightest contact from their points of attach- 
ment, and having been so, are so light as readily to be carried 
about by air-currents. One of the difficulties encountered in 
the study of dried sporangia is, in fact, dependent on their 
extreme lightness and the ease with which they are swept away 
by the air. This is not all, however; it is not only evident 
that a possibility for constantly recurring diffusion of the 
reproductive bodies by means of the air exists, but it also 
appears probable that when thus diffused they are more likely 
to undergo subsequent development than when diffused by the 
only other medium which can be supposed to play an influential 
part in the process—water. The more thoroughly dessicated 
the sporangia and spores are, the more are they capable of 
retaining their vitality under exposure to unfavorable con- 
ditions. When active, or when without being so, they have 
become softened and distended by immersion in passive fluids, 
they readily suecumb to influences which, when dried, they are 
capable of resisting with impunity for considerable periods. 
Now, there appears to be little reason to doubt that in the acid 
gastric fluids we have such unfavorable media, likely to act 
prejudicially on the reproductive bodies entering the digestive 
canal unless specially protected. Active or softened elements 
will thus probably fail to reach a locality favouring their further 
development, while those in a desiccated condition will pass on 
unaffected to assume activity in the lower portions of the 
digestive tube. 
In so far as the observations here recorded justify us in 
coming to a conclusion, the development of the parasite appears, 
