446 MEDICAL BOTANY. 



Several kinds of manna are described, but the only varieties that come to 

 this country, are the flake, and manna in sorts, the first of which is the 

 purest, though by no means the most purgative ; it is in irregular, unequal 

 pieces, rough, light, and porous, of a yellowish-white colour, with a crystal- 

 line or granular fracture, of a slight peculiar odour, and sweet taste. The 

 common or manna in sorts is in masses composed of whitish or yellowish 

 fragments, united together by a soft, tenacious, brownish matter ; this variety 

 has a nauseous taste, which is the greater, according to the preponderance of 

 the brown substance; where this latter forms the greatest portion, it has re- 

 ceived the name o£fat manna. Manna has been often analyzed ; it consists 

 of a peculiar sugar called Mannite, which is incapable of undergoing vinous 

 fermentation, Sugar, Purgative colouring matter, Gum, &c. 



The trees above noticed are not the only vegetables that furnish manna, or 

 a product analogous to it. Thus, according to Burckhardt and other travel- 

 lers in Arabia, the Bedouins make use of an exudation from the Tamarisk tree, 

 resembling this substance ; and that used in India is derived from a thorny 

 shrub, found in abundance in the Arabian and Persian deserts: it is the Al- 

 hagi maurorum ; a third kind is obtained from a species of Eucalyptus, 

 growing in Australia; it is also furnished by the Larix europcea, the Saliz 

 chilensis, &c. ; but none of these are equal to that from the Fraxinus. Man- 

 nite also exists in many vegetables, as in the celery, asparagus, melon, &c. ; 

 Ainslie (Mat. Ind. i.), after speaking of the various kinds of manna, observes, 

 " whether any of these mannas may be the product of the insect called Kermes 

 mannifera, I know not, but the inquiry might be interesting. Major Macdonald 

 Kinneir mentions, in his Geographical Memoir on Persia, a sort of manna 

 which the Persians call guz, and which may be procured in great quantities 

 in Louristan ; he adds, that it is obtained from a shrub, in appearance like a 

 fennel, about four feet high, and is supposed to be produced by small red 

 insects. These are seen in great quantities on the leaves." 



Medical Properties. — In small doses, manna is nutritive, and in large ones 

 laxative, and appears to increase in power with age; at least when first ga- 

 thered, it is said to be eaten in some quantity, without affecting the bowels. 

 The purest manna is not as purgative as the more inferior, for although man- 

 nite is laxative, the principal purgative principle resides in the brown viscous 

 matter. It is now seldom administered to adults, except in combination with 

 other substances, to disguise their taste, and also from the fact that when given 

 in any quantity, it is apt to cause flatulence and griping. It is, however, 

 much employed, especially in domestic practice, as a laxative for children. It 

 is given either in substance, or dissolved in warm milk or water. The dose 

 for an adult is from an ounce to two ounces, and for children, a drachm to 

 two or three. 



The bark of most of the species is bitter and astringent, and before the in- 

 troduction of Peruvian bark, was much employed in the treatment of inter- 

 mittent fevers; that most generally used was obtained from the F. excelsior, 

 and the evidence in favour of its curative powers is very great. It was also 

 recommended by Bergius as a febrifuge. The leaves are purgative, and are 

 spoken of by Coste and Willemet as nearly equal to Senna (Mat. Med. In- 

 digen. 36). The seeds, which are acrid and bitter, are said to be hydragogue 

 and diuretic. 





