THE STRUCTURE OF INSECTS. 



13 



digestive canal by osmosis, and mingle outside of this canal 

 with the currents of blood which pass along the ventral and 

 lateral parts of the body. 



Into the pyloric end of the stomach empty the urinary 

 tubes, their secretions passing into the intestine. These 

 organs are exclusively depuratory and urinary, relieving 

 the body of the waste products. The liquid which they se- 

 crete contains urea (?), uric acid, and urates in abundance, 

 hippuric acid (?), chloride of sodium, phosphates, carbonate 

 of lime, oxalate of lime in quantity, leuciue, and coloring 

 matters. 



The nervous system of the locust, as of other insects, con- 

 sists of a series of nerve-centres, or ganglia, which are con- 



FIG. 7. Digestive canal of Sarcophaga carnnr'n-. , salivary gland ; ?, oesoph- 

 agus; /, g, stomach; h, intestine; i, urinary tuues; fc, rectum. From Judeicu 

 and Nitsche. 



nected by two cords (commissures), the two cords in certain 

 parts of the body in some insects united into one. There 

 are in the locust ten ganglia, two in the head, three in the 

 thorax, and five in the abdomen. The first ganglion is 

 rather larger than the others, and is called the "brain." 

 The brain rests upon the oesophagus, whence its name, 

 supra-cesophageal ganglion. From the brain arise the large, 

 short, optic nerves (Fig. 8, op), which go to the compound 

 eyes, and from the front arise the three slender filaments 

 which are sent to the three ocelli (Fig. 8, oc). From im- 

 mediately in front, low down, arise the antennal nerves 

 (Fig. 4, at). 



The infra- cesophageal ganglion (Fig. 8, if), as its name 

 implies, lies under the cesophagus at the base of the head, 



