90 TTTE ANATOMY OF TTIK 1TONEY REE. 



3. THE AITIMENTAIJY CANAL. 



The alimentary canal is a tube Avhioh extends throuo^h the entire 

 length of the body and, on account of beings more or less coiled, it is 

 generally considerably longer than the length of the body in insects. 

 It has no openings of any sort into the body cavity. The internal 

 organs are packed closely about it, and the interstices are filled Avith 

 the blood, there being no special arteries or veins in insects. The 

 amount of space occupied by the alimentary canal varies according to 

 the amount, of food it contains, and for this reason it seldom looks 

 exactly alike in any two individuals examined. 



The part of the canal immediately following the mouth forms an 

 enlargement (fig. 42, PJnj) called the pharyn.r. Succeeding this, is 

 a slender tube which leaves the head by the foramen magnum above 

 the small transverse tentorial bar and traverses the entire length 

 of tlip thorax. This is the wsophagus {(E). In the anterior part of 

 the abdomen the (esophagus expands into a large thin-walled sac 

 which is ordinarily called the croj) or ingh/ries, but which, in the 

 bee, is known as the honey stomarh {IIS). Behind this is a short, 

 narrow, necklike division, with rigid walls constituting the pfo- 

 ventricnhts {Pvent). Then comes a large U-shaped part, with thick, 

 spongy-looking walls containing numerous annular constrictions. 

 This is the ventrieulns {Vent), or stomach, of the bee, frequently re- 

 ferred to as the " chyle stomach." Following the ventriculus is a 

 short, narrow, coiled small intestine {SIvt) having a circle of about 

 one hundred long, greatly coiled, blind, threadlike tubes opening into 

 its anterior nMid. These latter are called the Mut phjhhin tiil)iilps 

 {Med). Functionally they do not belong to the digestive tract, since 

 they are excretory organs, corresjKwding with the nei:)hridia of other 

 invertebrates and with the kidneys of vertebrates. Following the 

 small intestine is the J(f)r/e intestine, or reetirm {Rert). wliich is often 

 distended by its contents into a great sac occupying a large part of 

 the abdominal cavity. Six whitish bands on its anterior end are 

 called the reetal glands {RGl). The rectum opens to the exterior 

 through the anus, which is situated, as already described, at the end of 

 the rudimentary tenth or last segment of the abdomen (fig. 41, An). 



After this brief general survey of the parts of the alimentary 

 canal, we shall proceed with the description of each in detail, and at 

 the same time give what is known of the role each plays in the 

 process of digestion. ^\liat is known, however, about digestion in 

 the bee, or in any insect, for that matter, really amounts to nothing, 

 but the views of various writers on the subject must be discussed 

 briefly, in order to show how little has actually been demonstrated. 



The pharynx (figs. 11 R, 19, and 42, Ph;/) lies in the anterior part 

 of the head close behind the clypeus, extending from the mouth 



