66o 



THE POPULAR SCIENCE MONTHLY. 



grows, this organ is filled with a liquid which, in passing through 

 the spinners, the orifice of which you see, dries in the air, and forms 

 a thread. This thread constitutes the silk. 



The nervous system of the animal, placed below the digestive tube 

 is with insects, as with all animals, of the highest importance. It is 

 the nervous system which seems to animate all the other organs, and 

 particularly the muscles. The latter are what we call flesh or meat. 

 They are in reality the organs of movement, with our caterpillar as 

 with man himself. Each of them is formed of elementary fibres that 

 have the property of contracting and relaxing; that is to say, of 

 shortening and lengthening under the influence of the will and of the 

 nervous system. Upon this property depend all the movements exe- 

 cuted by any animal whatever. 



Fig. 2. 



Silk-secreting Apparatus of One Side of a Silk-worm. A, B, C, the part nearest the tail of 

 the worm, where the silk-matter is formed. D, E, enlarged portion reservoir of silky matter. 

 E, F. capillary tubes proceeding from the two glands, and uniting in one single short canal, F , 

 which opens in the mouth of the worm, at its under lip. Two silk threads are therefore 

 united together, and come out through the orifice with the appearance of a single thread. 



I wish you to remark, a propos of the caterpillar of this insect 

 that when crushed seems to be only a formless pulp that its muscular 

 system is admirably organized. It is superior to that of man himself, 

 at least, in relation to the multiplicity of organs. We count in man 

 529 muscles; the caterpillar has 1,64V, without counting those of the 

 feet and head, which give 1,118 more. 



In us, as in most animals, there exists a nourishing liquid par ex- 

 cellence that we know under the name of blood. This liquid, set in mo- 

 tion by a heart, is carried into all parts of the body by arteries, and 



