208 ENTOZOA FOUND IN MAN. 



be ascertained to be chiefly constituted by the agglo- 

 meration of an immense number of very minute 

 embryos, which are invisible to the naked eye, when 

 they are inspected singly. These embryos can live 

 for an indefinite period in water at the ordinary 

 temperature of European countries, and they are 

 capable of exhibiting lively movements after they 

 have been kept dry for many hours, if they are 

 again moistened with water. ^ 



It is, therefore, probable that, at the heat which 

 is always maintained in intertropical countries, these 

 embryos may hve for a long period in water at a 

 high temperature, and may also remain in a state of 

 desiccation for a considerable space of time without 

 the loss of their vitality. These points have not been 

 fully investigated ; but, whatever may be the extent 

 of the property which the embryo possesses of living 

 for a certain period out of the human body, it is 

 certainly to it that the Guinea-worm owes its means 

 of transmission ; in fact, the larvae, either living in 

 the water of the lakes or rivers, into which they 

 have been carried through the medium of the dust, 

 or revivified by the agency of the rain when they are 

 situated upon the soil, may after a long interval be 

 placed in a position suitable to their introduction 

 into the tissues where they subsequently become 

 developed. 



The question has been raised, whether the em- 

 bryos which are expelled from the body of the 

 parent-filaria can at once introduce themselves into 



^ Similar phenomena have been observed in the embryos of 

 certain small nematoid worms which live in insects like the filarise 

 do in man. 



