HISTOLOGY OF THE DIGESTIVE CANAL 321 



The third division (intestine and rectum) is composed of an epithe- 

 lium, the cells of which are intermediate in size between those of the 

 fore and mid gut. The cells are often pigmented, and they are 

 covered by a much thicker cuticula than that of the stomach, but 

 which is not so thick and hard as that of the oesophagus and pro- 

 ventriculus. The very refringent cuticula is not thrown up into 

 ridges, though in some parts it is covered with delicate conical 

 spi'nes, which are very short. " The epithelium and underlying con- 

 nective tissue (tunica propriety are thrown up into six folds, which 

 run longitudinally, being regular in the ileum and rectum (as the 

 rectal glands), but very irregular in the colon. Outside the depres- 

 sion between each two neighboring folds there is a longitudinal 

 muscular band, these making six bands. This peculiar disposition 

 of the longitudinal muscles does not occur in any other part of the 

 canal ; it is, therefore, especially characteristic of the third divi- 

 sion." (Minot.) 



LITERATURE ON THE ORGANS OF DIGESTION 



Treviranus, G. R. Resultate einiger Untersuchungen iiber den inneren Bail 



der Insekten. (Verdauungsorgane von Cimex ritfipes.) (Annal. d. Wet- 



terau. Gesells., 1809, i, pp. 169-177, 1 Taf.) 

 Ramdohr, C. A. Abhandlungen iiber die Verdauungswerkzeuge der Insekten. 



1811, vii, pp. 221, 30 Taf. 

 Dutrochet, R. J. H. Me"moire sur les metamorphoses du canal alimentaire dans 



les insectes. (Journal de Physique, 1818, Ixxxvi, pp. 130-135, 189-204; 



Meckel's Archiv, 1818, iv, pp. 285-293.) 

 Suckow, F. W. L. Verdauungsorgane der Insekten. (Heusinger's Zeitschr. f. 



organ. Physik., 1828, iii, pp. 1-89.) 

 Doyere, L. Note sur le tube digestif des Cigales. (Ann. Sc. nat. Zool., 1839, 



2 Se>., xi, pp. 81-85.) 

 Grube, A. E. IVb.lt den Wespen- oder Hornissenlarven ein After oder nicht? 



1 Taf. (Miiller's Archiv fur Physiol., 1849, pp. 47-74.) 

 Sirodot. Recherches sur les secretions chez les insectes. (Ann. Sc. nat. Zool., 



1858, 4 Se>., x, pp. 141-189, 251-328, 12 Pis.) 



Milne-Edwards, H. Le<jons sur la physiologic et Panatomie compared, v, 



1859, pp. 498-536, 581-638. 



Dufour, L. Recherches anatomiques sur les Carabiques et sur plusieurs autres 

 insectes Cole"opteres. Appareil digestif. (Ann. Sc. nat,, ii, 1824. pp. 

 462-482, 2 Pis. ; iii, 1824, pp. 215-242, 5 Pis., pp. 476-491, 3 Pis. ; iv, 1824, 

 pp. 103-125, 4 Pis. ; iv, 1825, pp. 265-283.) 



Recherches anatomiques sur PHippobosque des chevaux. (Ann. Sc. nat., 



1825, vi, pp. 299-322, 1 PI.) 



Description et figure de 1'appareil digestif de VAnobium striatum. (Ibid., 



xiv, 1828, pp. 219-222, 1 PI.) 



Recherches anatomiques sur les Labidoures. Appareil de la digestion. 



(Ibid., xiii, 1828, pp. 348-354, 2 Pis.) 



Y 



