368 PHYSIOLOGY. 



we find a family which agrees entirely with the Lepidoplera in requiring 

 but little food, viz. the Capricorn beetles. They also, as beetles, 

 probably eat but little; at least, in all those individuals that I have dis- 

 sected, I found the intestine full of air ; and their nutriment likewise 

 consists of the delicate nectareous juices of flowers. But of all 

 haustellate insects the Diptera are the most voracious : we observe 

 them the whole day long lapping and tasting every possible substance 

 which contains sweet juices, or such as are agreeable to their palate, and 

 which are frequently nauseous and stinking. They have consequently 

 the longest duodenum of all insects. In front, where it supplants the 

 stomach, it is most compact and muscular ; behind it is softer, more 

 delicate and membranous. The food is received into this long intestine, 

 and, as it is generally of a cruder nature than that of the Lepidoptera, 

 it consequently requires several different elaborative fluids. We there- 

 fore find, besides the oral salivary glands, others which sink into the 

 commencement of the duodenum. 



222. 



The elaboration of chyle takes place even in the first portion of the 

 intestine, which corresponds in situation with the stomach and ilium, 

 or where a proventriculus is found only in the duodenum lying behind 

 it. The chyle is a whitish or greenish or even brownish, thick liquid, 

 which first presents itself as a flocky substance between the innermost 

 and second tunics of the stomach, and, upon a microscopic inspection, 

 appears to consist of minute globules. It is the produce of digestion and 

 the object of all the functions of the intestinal canal, and it forms the 

 foundation of all the other nutritive fluids. In the higher animals, the 

 chyle is therefore absorbed by the lymphatic vessels placed along the 

 intestine, and conducted into the venous blood, whence it passes into 

 the lungs or gills, here becoming oxydised, and it is then poured forth 

 by the heart as fresh arterial blood. But such a circulation of the 

 juices is not found in insects, for they have neither absorbents nor veins, 

 but merely a single arterial vessel placed along the back. If, therefore, 

 the chyle or lymph is to pass into this vessel, it must be transmitted 

 through the parietes of the intestine and pass through the cavity of the 

 stomach, whence the heart receives it through the above-described 

 valve. This passage of the chyle through the intestinal tunic 

 observation has distinctly detected. Ramdohr saw the chyle which 

 was contained between the mucous membrane and the true skin forced 



