70 DIRECT BENEFITS FROM MOTHS. 



thread. She fixes the first drop of gum that issues, 

 where she pleases, and then draws back her head, or 

 lets herself fall, while the gum, continuing to flow, is 

 drawn out and lengthened into a double (single, 

 according to Lyonnet) stream. Upon being exposed 

 to the air, it immediately loses its fluidity, becomes 

 dry, and acquires consistence and strength. She is 

 never deceived in adjusting the dimensions of the 

 (united) apertures, or in calculating the proper thick- 

 ness of the thread, but invariably makes the strength 

 in proportion to the weight of her body. 



" It would be a very curious thing to know how 

 the gum which composes the silk is separated and 

 drawn off from the other juices that nourish the 

 animal. It must be accomplished like the secretions 

 formed by glands in the human body. I am, there- 

 fore, persuaded that the gum bags of the Silk Worm 

 are furnished with a set of minute glands, which, 

 being impregnated with gum, afford a free passage to 

 all the juices of the mulberry leaf corresponding with 

 the glutinous matter, while they exclude every fluid 

 of a different quality."* If this theory be correct, 

 then it applies equally to all the silk-spinning cater- 

 pillars. 



" Spectacle de la Nature, vol. i. 



