80 Silk Manufacture. 



vessels. According to the different proportion of the elements 

 which compose the leaf, it follows, that cases may occur in 

 which a greater weight of leaf may yield less that is useful to 

 the silk worm, as well for its nourishment, as with respect to 

 the quantity of silk obtained from the animal." 



' To complete the developement of the silk worm, the quan- 

 tity of leaves consumed must bear relation to the nutriment 

 they contain. It is therefore important that leaves contain- 

 ing the most nutriment should be supplied to the insect, as it 

 is more fatigued and more liable to disease from devouring 

 many leaves, than it would be if an equal quantity of nourish- 

 ment were supplied by fewer leaves containing more saccha- 

 rine substance. Again, if this abounds in the leaf, and the 

 resinous substance is not found united with it in sufficient 

 quantity, the worm will, it is true, thrive and grow, but will 

 not produce silk proportionate to its weight. 



'In some parts of Italy and France, mulberry leaves are 

 commonly sold by weight in the market, and those who rear 

 silkworms are often wholly dependant on this source for sup- 

 ply. Judgment and experience are required in the purchaser, 

 to enable him to make a proper selection of leaves, choosing 

 such as are of a nourishing quality, and rejecting those whose 

 sale would, from their greater weight, be more profitable to 

 the vender. The interest of the two parties are consequently 

 at variance. In other places, trees are hired for the season ; 

 from four to six francs, according to its size and condition, 

 being paid for the hire of each tree. Under eqiial circum- 

 stances, an old mulberry tree always yields better leaves than 

 a young one ; and whatever may be the original quality of 

 the tree, as it grows older the leaf will diminish in size, and 

 will so materially improve, that at length it will attain to a 

 very excellent quality. 



' It is of importance that the age of the leaves should keep 

 pace with that of the worms. The young leaf, being replete 

 with aqueous matter, provides for the great evaporation con- 

 tinually proceeding from the body of the young worm ; while 

 the mature leaf contains a larger proportion of solid nutritive 

 matter, better suited to the wants of the insect at its more 

 advanced age. To give old leaves to young worms, or young 

 leaves to old worms, would be alike prejudicial. 



' The greatest care must be taken to prevent the leaves ^ 



becoming heated or fermented. The nutritious substance of ^ 

 the leaf is altered and injured by the slightest fermentation, 

 and it becomes too stimulating for the health of the worm. It 

 is also essential that the leaves be given to the insects per- 

 fectly dry ; contagious and fatal diseases will otherwise ensue. 



