2 THE AMEEICAN MONTHLY [January, 



but, unlike the furnace, an active organ has power to 

 arrest the burning and rebuild itself, provided food is given 

 in time. When the w^ork is done and the products of 

 burning are formed, they must be removed while the gaseous 

 carbonic acid escapes through the respiratory system ; the urea 

 being fluid, is taken up by the malpighian tubes and poured into 

 the alimentary tube, wlience it escapes with the fceces. In ver- 

 tebrate animals the organ for removing urea is called a kidney, 

 and has no connection with the alimentary tube. The alimen- 

 tary, circulatory, respiratory, and excretory systems of the grass- 

 hopper are tributary to the muscular, nervous, and reproductive 

 systems. 



5. The muscular system is composed of organs called muscles. 

 These are small strips of living substance which have the peculiar 

 property of shortening or contracting whenever they are excited 

 or sthnulated to do so. In the grasshopper they are fastened 

 across joints from bone to bone by tendons in such a way that by 

 contracting and pulling on the tendon the joint can be bent or 

 straightened. The muscles of the hind leg can be easily seen 

 (Fig. 4) by opening the legs and two tendons found so fastened 

 to the tibia that one bends it on the femur and the other straightens 

 it. The same is true for the wings, the mouth-parts, etc., and the 

 walls of the alimentary tube and heart contain the same kind of 

 contractile substance which, by its contraction, causes movement 

 of the substances contained within the tube. The number of separ- 

 ate muscles in a grasshopper's body is very great ; by their com- 

 bined uses in various walls all the exact and beautiful motions of 

 the animal are brought to pass. Thus a jump is produced by the 

 straightening of the femur-tibia joint in both hind legs at once, 

 while walking is due to the conjoint action of all six legs in alter- 

 nating sets, some going forward while others are going back. 

 The beautiful adjustment of tension at each of the very many 

 joints involved in such an act is regulated in the nervous system. 



6. The nervous system in the grasshopper is composed of or- 

 gans called ganglia and nerve cords, some of which connect the 

 ganglia into a chain, while others run direct from the ganglia to 

 the various adjacent portions of the body. The principal ganglia 

 of the body form a row or series extending from the head to the 

 tail ; the front one or drain lies in front of the throat, and sends 

 nerves to the organs of the head, and a pair which pass as a collar 

 on either side of the throat and run back to the prothorax. The 

 remaining nerves are on the ventral side of the body, just inside 

 the sterna, and are called tiie ventral nerve cord, and there are 

 one in each thoracic somite and five in the abdomen. The nerve 

 ganglia are the seats from wliich nerve stimuli are sent out over 

 the nerve fibres or cords which carry the stimuli to the active or- 

 gans. It is the brain which is the chief seat of nerve action, and 

 also the part whose perfect health and action are necessary to what- 

 ever intelligence the grasshoj^per may possess. That it has some 



