23 



founded even by Scheele, for apples contain a portion of sorbic as 

 well as of malic acid ; but that these acids are different, Mr. Donovan 

 proves by decomposing malate of lead by sorbic acid. For if water 

 be boiled on malate of lead, no crystals are to be obtained on cooling 

 the liquor ; but when the malate is boiled in sorbic acid, the malate 

 is decomposed ; and the liquor, when cooled, deposits the peculiarly 

 brilliant crystals of sorbate of lead. 



In order to be well assured of the difference between these acids, 

 Mr. Donovan compared his acid with as many as seven different spe- 

 cimens of malic acid obtained from different sources, and was con- 

 firmed in the opinion that they are essentially different, by comparison 

 of various neutral salts obtained from each ; those containing sorbic 

 acid being in general to be procured in permanent crystals, while 

 those from malic acid yield merely deliquescent residua when reduced 

 to dryness. 



The author remarks, that the purest malic acid is that prepared 

 from the Sempervivum tectorum, which, according to the observation 

 of Vauquelin, appears to be free from every other acid ; while the 

 juice of apples, unless they be taken very young, appears constantly 

 to contain a portion of sorbic acid. 



This paper concludes with conjectures respecting the progressive 

 changes of vegetable products, and possible conversion of bitter prin- 

 ciple into malic acid, sorbic acid, and oxalic acid ; but the author is 

 fully sensible that little reliance can be placed on such speculations. 



On the Structure of the Organs of Respiration in Animals which ap- 

 pear to hold an intermediate Place between those of the Class Pisces 

 and the Class Vermes, and in two Genera of the last -mentioned Class. 

 By Sir Everard Home, Bart. V.P.R.S. Read June 1, 1815. [Phil. 

 Trans. 1815, p. 256.] 



The genera of animals here enumerated by the author, are the 

 Lamprey, Myxine, an animal between the Lamprey and the Myxine, 

 the Aphrodita aculeata, and the Leech. 



In the Lamprey, the organs of respiration consist of separate oval 

 bags, that have seven openings on each side of the neck, for receiv- 

 ing and emitting the water which they breathe by means of a carti- 

 laginous thorax surrounding the bags. In the Lampern, which is of 

 the same genus, the structure is very similar, but the cartilages of 

 its thorax are weaker. 



In an animal brought from the South Sea by Sir Joseph Banks, 

 there are also the same number of external openings, and the same 

 number of bags ; but there is no cartilaginous thorax, and hence the 

 author is induced to consider the animal intermediate between the 

 Lamprey and Myxine, which it resembles in having teeth, and in hav- 

 ing a mesentery to its intestines. 



In the Myxine, there are only two orifices on the under surface of 

 the neck ; but these branch internally to six separate bags on each 

 side. 



