49 



cipal blood-vessels of the lung, and even in the heart itself; and the 

 venous sinuses at the base of the brain and the cavity of the tympa- 

 num were literally clogged with Strongylus minor. Now we cannot 

 but imagine that any animal so infested must, as a necessary conse- 

 quence, have both the functions of respiration and circulation greatly 

 impeded. Three porpoises which I have dissected within the last 

 two months, have all contained Entozoa, and all these were taken 

 in the Thames ; and it is probable that this may be the reason of their 

 leaving the ocean and running up the rivers at particular seasons of 

 the year, and it would be curious to ascertain whether those taken at 

 sea about the same period were so infested. Some light, I trust, may 

 be thrown on the occurrence of Entozoa in particular parts of an ani- 

 mal, when we have them, as in this instance, actually living in the 

 blood. We can now readily imagine how the young, when emitted 

 from the parent, can be transported to all parts of the body by means 

 of the circulation, and analogy would lead us to conclude that the 

 blood of other animals may contain Entozoa, as well as that of the 

 porpoise. There is another curious circumstance connected with 

 these Strongyli : — all the specimens of the four species just described 

 are nearly constant in their size, we meet with no young ones amongst 

 them ; these probably are to be found in parts of the body where the 

 scrutinizing eye of the anatomist has as yet failed in detecting them. 

 But however, this is mere matter of speculation ; and I will no longer 

 detain the Society on a subject which, from time immemorial, has 

 been to reflecting minds a wonder, how Entozoa " live, and move, 

 and have their being." 



TRANS. MIC. SOC. VOL. I. 



