588 PRACTICE OF PHYSIC. 



the nature and production of these vesicles ; but the [matter 

 at last seems to be ascertained. It seems to be certain, that 

 each of these vesicles has within it, or annexed to it, a living 

 animal of the worm kind ; which seems to have the power of 

 forming a vesicle for the purpose of its own economy, and of 

 filling it with a watery fluid drawn from the neighbouring parts ; 

 and this animal has therefore been properly named by late na- 

 turalists, the Tcenia hydatigena. The origin and economy of 

 this animal, or an account of the several parts of the human 

 body which it occupies, I cannot prosecute further here ; but 

 it was proper for me, in delivering the causes of dropsy, to say 

 thus much of hydatides ; and I must conclude with observing, 

 I am well persuaded, that most of the instances of preternatural 

 encysted dropsies which have appeared in many different parts 

 of the human body, have been truly collections of such hyda- 

 tides ; but how the swellings occasioned by these are to be dis- 

 tinguished from other species of dropsy, or how they are to be 

 treated in practice, I cannot at present determine. 



MDCLXIII. After having mentioned these, I return to 

 consider the other general cause of dropsy, which I have said in 

 MDCXLVI. may be, an interruption or diminution of the ab- 

 sorption that should take up the exhaled fluids from the several 

 cavities and interstices of the body ; the causes of which inter- 

 ruption, however, are not easily ascertained. 



MDCLXIV. It seems probable, that absorption may be di- 

 minished, and even cease altogether, from a loss of tone in the 

 absorbent extremities of the lymphatics. I cannot indeed doubt 

 that a certain degree of tone or active power is necessary in these 

 absorbent extremities ; and it appears probable, that the same 

 general debility which produces that laxity of the exhalent ves- 

 sels, wherein I have supposed the hydropic diathesis to consist, 

 will at the same time occasion a loss of tone in the absorbents ; 

 and therefore that a laxity of the exhalents will generally be 

 accompanied with a loss of tone in the absorbents ; and that this 

 will have a share in the production of dropsy. Indeed it is prob- 

 able that the diminution of absorption has a considerable share 

 in the matter ; as dropsies are often cured by medicines which 

 seem to operate by exciting the action of the absorbents. 



MDCLXV It has been supposed, that the absorption per- 



