Egypt, with shining spots on their backs, which may be termed Lice there, and may be different not only from the common Louse, but from the Louse mentioned by Moses as one of the plagues of Egypt, which is admitted to be a filthy troublesome Louse, even worse than the said Louse, which is clearly different from the Louse libelled.  But that the other Louse is the same with, or similar to, the said Beetle, which is also the same with the other Beetle; and although different from the said Beetle libelled, yet, as the said Beetle is similar to the other Beetle, and the said Louse to the other Louse libelled; and the other Louse to the other Beetle, which is the same with, or similar to, the Beetle which somewhat resembles the Beetle libelled; assoilzies the defender, and finds expenses due.’

     “Say away, my Lords.

“LORD MEADOWBANK.—­This is a very intricate and puzzling question, my Lord.  I have formed no decided opinion; but at present I am rather inclined to think the interlocutor is right, though not upon the ratio assigned in it.  It appears to me that there are two points for consideration. First, whether the words libelled amount to a convicium against the Beetle; and Secondly, admitting the convicium, whether the pursuer is entitled to found upon it in this action.  Now, my Lords, if there be a convicium at all, it consists in the comparatio or comparison of the Scaraboeus or Beetle with the Egyptian Pediculus or Louse.  My first doubt regards this point, but it is not at all founded on what the defender alleges, that there is no such animal as an Egyptian Pediculus or Louse in rerum natura; for though it does not actually exist, it may possibly exist (if not in actio, yet in potentia—­if not in actuality, yet in potentiality or capacity); and whether its existence be in esse vel posse, is the same thing to this question, provided there be termini habiles for ascertaining what it would be if it did exist.  But my doubt is here:—­How am I to discover what are the essentia of any Louse, whether Egyptian or not?  It is very easy to describe its accidents as a naturalist would do—­to say that it belongs to the tribe of Aptera (or, that is, a yellow, little, greedy, filthy, despicable reptile), but we do not learn from this what the proprium of the animal is in a logical sense, and still less what its differentia are.  Now, without these it is impossible to judge whether there is a convicium or not; for, in a case of this kind, which sequitur naturam delicti, we must take them meliori sensu, and presume the comparatio to be in melioribus tantum.  And here I beg that parties, and the bar in general—­[interrupted by Lord Hermand:  Your Lordship should address yourself to the Chair]—­I say, I beg it may be understood that I do not rest my opinion