/OOLOGY FOR MKDICAL STUDENTS 



CHAP. 



s.o.g. 



n.c. 



{)h . u onwards by what are termed peristaltic contractions 



ot - ti wall, waves of constriction produced by the contraction 



in succession of the circular 

 muscles passing tailwards 

 and pushing the contained 

 food in the same direction. 

 In the gizzard, where the 

 muscular coat is specially de- 

 veloped, the food undergoes a 

 process of grinding into pulp. 

 The food during its onward 

 progress is subjected to the 

 action of various secretions. 

 The actual process of diges- 

 tion is mainly carried out in 

 the intestine and the digestive' 

 ferments are produced by 

 gland-cells which are scattered 

 about in the endoderm arid 

 pour their secretions into the 

 intestinal cavity. In the region 

 of ' the oesophagus (about seg- 

 ments X-XII) special collec- 

 tions of gland-cells are found 

 in three pocket-like outpush- 

 ings of the enteric wall (Fig. 

 65, A, c.g). These are the 

 caleiferous glands, so called 

 from the nature of their secre- 

 tion calcium carbonate 

 which gives the glands a very 

 characteristic white chalky 

 FIG 6 appearance. The function of 



Diction, <ri /./,, seen from the donal side. this secretion is apparently to 



neutralize the free acid so 

 frequently present in the soil 

 which the worm ingests. 



Between the enteric wall 

 and tin- body wall is the wide body-cavity or coelome (Fig. 63, 

 coel), divided into numerous compartments one to each somite 

 y thin transverse membranous partitions or septa, and 



A, to show alimentary canal ; B, to show . 

 nervous system, an. Anus ; /.., , hurral r.ivity ; c, crop ; 

 c.g, c-ii . ; /,, Ki/./.inl ; int, intrstii; 



nerve-cord; oes, oesophagus; ph, pharynx; s.o.g, 

 supra -oesophageal gan 



