424 ESSENTIALS OF ZOOLOGY 



divided into a number of chambers with side valves, which allows 

 the blood to enter but not to escape, except through the vessel 

 toward the head. Due to the pulsating of this portion of the tube, 

 which has been called the heart, the blood is forced to the anterior 

 part of the body where it flows out into the body cavity and slowly 

 returns to the abdominal region. In this process the tissues are 

 supplied with nourishment from the food materials carried in the 

 blood. It will be noted that the circulatory system has practically 

 nothing to do with the carrying of oxygen to the tissues. 



The digestive system of the grasshopper consists of a practically 

 straight tube extending from the mouth to the anus through the 

 central portion of the body. The food after being ground up by the 

 mouth parts passes into the mouth or pharynx where it is mixed 

 with the salivary mucin, and the action of the enzyme, invertase, 

 begins. From the mouth the food is conveyed through the esopha- 

 gus to the crop and gizzard which are dilatations of the tract filling 

 a great portion of the thorax. The gizzard is muscular and lined 

 with chitinous ridges which strain the coarse particles of food and 

 prevent their entering the next division of the system, the stomach. 

 The food is acted upon in the stomach by the secretions of the gas- 

 tric caeca, which are glandular bodies opening into the anterior 

 end of the stomach. They secrete a weak acid which helps in the 

 emulsification of fats and the conversion of albuminoids into pep- 

 tones. Much of the food is absorbed into the hemolymph from the 

 stomach. Between the stomach and the intestines is a pyloric valve 

 which permits the contents of the system to pass in only one direc- 

 tion. In the intestine, which is divided into the ileum, colon, and 

 rectum, absorption of food continues, especially in the ileum. Just 

 back of the stomach many threadlike tubes enter the intestine. These 

 tubes are the excretory organs, known as Malpighian tubules, and 

 perform a similar function to that of the kidneys of higher animals. 

 The rectum has thick muscular walls with six-surface rectal glands. 

 The feces are expelled from the rectum to the outside of the body 

 through the anus. 



The nervous system consists of a series of ganglia or nerve cells 

 connected by a double set of commissures or connecting nerve fibers 

 lying along the ventral body wall. Five ganglia are located in the 

 abdomen. Since there are at least eleven segments in the abdomen 

 of the adult grasshopper, it is apparent that the ganglia of some of 



