CONSTITUENTS OF PLANTS, ETC. 337 



from the nectaries of flowers and deposits it in its honey- 

 bag, which is really a crop connected with the gullet. Dur- 

 ing the time that it remains there it is probably acted upon 

 by the secretions of the mouth and the crop ; so that when 

 the bee, on its return, disgorges it into some honey-cell in 

 the hive, it is probably not exactly of the same chemical 

 composition as when it was first collected from the flowers. 

 Honey varies much in its qualities, from the coloring and 

 odoriferous substances of different plants, which become in- 

 timately combined with the honey as the bee gathers it. 

 Some honeys are for this reason much more highly valued 

 than others. 



466. Manna. There are various trees from which sub- 

 stances called manna are obtained. In these substances 

 there is a peculiar sugar called mannite C 6 H 14 O 6 which 

 is less sweet than even the grape-sugar. There is also in 

 them some sugar which appears to be like grape-sugar, and 

 also some other matters. The composition of the ordinary 

 manna of commerce may be stated thus : 



Per Cent 



Mannite 40 



Grape-sugar 10 



Gum and other matters. 40 



Water 10 



100 



The large proportion of gum and other matters in the 

 manna lessens, of course, its sweetening capacity. When 

 freshly gathered it is very agreeable to the taste, and is a 

 valuable article of food. But after it has been kept for 

 some time it has a laxative quality which unfits it for use 

 as food. This medicinal quality is not owing to the sugar, 

 but to some chemical change in the other substances. A 

 manna obtained from a tree in the neighborhood of Mount 

 Sinai is supposed by some learned men to be the same as 



P 



