48 On Ciiric Acid. 



other part of the head gives a vapour, and I know not any other 

 part except the lungs from which air may be drawn in this pe- 

 culiar manner. Tliat Cuvier was perfectly wrong in supposnig 

 this part to be the intestines of the zoophyte is certain ; the brain 

 has that peculiar shape which no other part in the smallest degree 

 resembles, and which is alike in all animals, insects, zoophytes, 

 &:c. I was indeed most anxious to prove whether the actenia 

 possessed a bruin and nvrve^ ; for I never yet saiv or dissected 

 an insect (ever so small) torpid or insignificant that had noi 

 those parts ; or any being that deserved i.he name of a feeling 

 animal, which had not both brain and nerves ; for surely the 

 being that is sensible of pain or pleasure, must have those parts, 

 from which those feelings result ; and as there is in each part, 

 that peculiar ??;flr^, which distinguishes them when seen, they can- 

 not be mistaken : thus the nuiscle is known by its contracting 

 poiver, by its increasing hardness when cut, and by its visinsita 

 possessed by no other part of the body, in either insect, animal, 

 plant, or human being. The nerve is known by its being that 

 remarkable link which is the source or vehicle of communication 

 between the brain and muscle ; and serving probably as a pass- 

 age for that ga«, which mav produce so many curious pheno- 

 mena in the human frame, wliile the brain is that peculiar formed 

 matter which in every creature that feels, has the same appear- 

 ance and consistency, and may always be likened to a great fat 

 worm. 



I am, sir, 



Your obliged servant, 

 Exeter, July 19, 1815. AgnES IbbETSON. 



XVI. On Citric Jcid. J5m Samuel Paukks, F.L.S.A/.G.S. 



X HERE is a peculiar acid in the juice of lemons, citrons, limes, 

 and a variety of other fruits, different in some of its proper- 

 ties from all others, and known to chemists by the name of ci- 

 tric acid. The ancients, it appears, made no use of the juice 

 of these fruits except as an antidote against poison. Formerly 

 the citric was supposed to be identical with the tartaric acid j 

 but the citric acid does not decompose muriate of potash, nor 

 •ulphate of lime, like oxalic acid. Georgius in the Stock- 

 holm Memoirs proposed the separation of this acid from the 

 mucilage of the juice by cold ; but the ingenious iScheele was the 

 first who exhibited this acid in a solid form. To accomplish this, 



* From tlie "Chemical Essays," in 5 vols. 12mo. just published ; and of 

 \»hich vve shall give an analysis in our next. 



lie 



