218 ANIMAL PHYSIOLOGY. [LESSON 64. 



949. A carefully compiled description has thus been given of the 

 form of the nutrimental organs, and their accessory glandular ap- 

 pendages, in the several classes of the animal kingdom, commencing 

 with the lowest, and tracing its gradual development up to man. 



LESSON LXIY. 



NUTRITION IN MAN, CONTINUED. 



950. In the class of ANIMALCULA, we saw a number of digestive 

 cavities possessing but one opening ; a little higher in the same class, 

 this cavity was extensively sacculated. 



951. In the KOTIFEROUS animals, the alimentary canal possesses 

 two openings, and a glandular apparatus is superadded. 



952. The ENTOZOA (intestinal parasites) are somewhat anomalous ; 

 the Acephalocyst, although allied to the Entozoa by its affinities, is 

 really lower than the lowest animalcule. It is provided with a nu- 

 trimental cavity, but destitute even of a mouth, and like the plants, 

 to which it is most closely allied, propagated by spontaneous division. 

 None of the Entozoa possess more than one cavity to their nutri- 

 mental organs. 



953. In the POLYPI we found the same simple condition of the 

 nutrimental canal, and in those which possess a stomach with two 

 cavities, the lower one is solely devoted to the transmission of nutri- 

 ment for the extension of the commonwealth. 



954. The ACALEPHA are equally simple, and the like must be said 

 of some of the 



955. ECHINODERMATA, where Asterias possesses only one diges- 

 tive aperture. 



956. In the remaining orders, a slight advance has been made ; 

 the alimentary canal is much more extensive, possesses convolutions, 

 and terminates in a distinct aperture, opposed to the mouth. 



957. Amongst the lowest of the ANNELLIDES ranks the Leech ; 

 but although possessing only a stomach furnished with ccecal append- 

 ages, it has yet two apertures. The Aphrodita, in addition to its 

 numerous ccoca, has an intestine superadded. 



958. In the lowly EPIZOA, we still have two apertures to the ali- 

 mentary canal, in addition to an intestine, which indicates a higher 

 grade of development. 



