286 THE NATURE AND TREATMENT OF 



ova which show no sign of any approach of degeneration or 

 decay. And the writer of this review has been struck by the 

 remarkable way in which the size and structure of these ova 

 allow them to elude all precautions that may be taken against 

 their mechanical dispersion. In spite of every attempt to in- 

 sure their destruction, by steeping the specimen glasses he may 

 have used in strong acids, and by afterwards bathing them in 

 the flame of a spirit-lamp, he has once or twice found the 

 characteristic ova appear most unaccountably in healthy and 

 diseased tissues of secretions of the human body, which he 

 has subsequently examined with these glasses. The dissolution 

 of the parent tissues ultimately sets free the eggs contained in 

 their interior, to be carried by the winds and waves wherever 

 accident may determine. How vast a number of them miscarry, 

 is evident when we attempt to take the census of a single tape- 

 worm. Or, imagine the million of eggs such a parent foists 

 upon society during the years it may inhabit a given animal. 

 What becomes of these abortive germs, how long they retain 

 any vitality, and what are the circumstances that may rob 

 them of it, are questions we cannot- answer, save by the con- 

 jecture that their albuminous and fatty materials are either ap- 

 plied to the soil in a decomposed form, or are consumed as food 

 by various of the minute intervertebrata that throng the sur- 

 face of the earth and the waters. But the more fortunate 

 minority of these eggs, the destiny of which is to eat instead of 

 being eaten, after many and long wanderings of this passive 

 nature, are at length engulfed by some unconscious animal in 

 company with its food, and through its alimentary canal attain 

 the locality of their second form of existence. During this 

 passive emigration, the worm has retained its previous size 

 (l-700th of an inch) and shape. But its thick wall bursts 

 and sets free the inclosed embryo, which is an ovoid body, of 

 nearly equal size, armed with six booklets at one extremity. 

 Impelled by instinct to begin its active migration, the embryo 

 pierces the first portion of its path, by bringing together the 

 anterior pair of hooks so as to form with them a kind of wedge- 

 shaped stiletto, and now drags itself forward in the same 



