138 VESTIGES OE THE 



is in nothing placed in greater difficulties than it is with 

 regard to the entozoa, or creatures which live within the 

 bodies of others. These creatures do, and apparently 

 can, live nowhere else than in the interior of other living 

 bodies, whei-e they generally take up their abode in the 

 viscera^ but also sometimes in the chambers of the eye, 

 the interior of the brain, the serous sacs and other places 

 having no communication from without. Some are vivi- 

 parous, others oviparous. Of the latter it cannot reason- 

 ably be supposed that the ova ever pass through the 

 medium of the air, or through the blood-vessels, for they 

 are too heavy for the one transit, and too large for the 

 other. Of tlie former, it cannot be conceived how they 

 pass into }'oung animals — certainly not by communica- 

 tion from tht! parent, for it has often been found that 

 entozoa do not appear in certain generations of a human 

 family, and some of peculiar and noted character have 

 only appeared at rare intervals, and in very extraordinary 

 circumstances. A candid view of the less popular doc- 

 trine, as to the origin of this humble form of life, is taken 

 by a distinguished living naturalist. ''To explain the 

 beginning of these worms within the human body, on 

 the common doctrine that all created beings proceed from 

 their likes, or a primordial Q^g^ is so difficult, that the 

 moderns have been driven to speculate, as our fathers did, 

 on their spontaneous birth ; but they have received the 

 hypothesis with some modification. Thus it is not from 

 putrefaction or fermentation that the entozoa are born, 

 for both of these processes are rather fatal to their exist- 

 ence, but from the aggregation and fit apposition of 

 matter which is already organised, or has been thrown 



from organised surfaces Their origin in this 



manner is not more wonderful oi- more inexplicable 

 than thai of many of the inferior animals from sections 



