SILK-PBODUCING OKGANS. 101 



little knobs are called "ganglia," each forming a 

 nervous centre, from which smaller nerves radiate to 

 the different portions of the body. 



As for brains, the caterpillar dispenses with them 

 almost entirely ; and instead of wearing one large 

 brain in the head, is furnished with a row of lesser 

 brains, or ganglia, extending through its whole 

 length. This is the reason why caterpillars are so 

 tenacious of life. If a man loses his head, he dies 

 immediately ; but an insect is not nearly so fastidious, 

 and continues to live for a long time without any 

 head at all. Indeed, there are some insects, which, 

 if beheaded, die, not so much on account of the head, 

 but of the stomach : for, having then no mouth, they 

 cannot eat, and so die of hunger. And some insects 

 there are which positively live longer if decapitated 

 than if left in possession of their head. 



On the right hand may be seen a curiously twisted 

 organ, marked c, swelling to a considerable size in 

 the middle, and diminishing to a mere thread at each 

 end. This is one of the vessels that contain the silk, 

 or rather the substance which becomes silk when it 

 is spun. 



If this organ be cut open in the middle, it will 

 be seen filled with a gummy substance of curious 

 texture, partly brittle and partly tough. From this 

 substance silk is spun, by passing up the tube, 

 through the thread-like portion, and so at last 

 into a tiny tube, called the spinneret, which opens 



