THE COCKROACH. 355 



larly studied by Bascli. 1 From the oral cavity to the funnel- 

 shaped extremity of the proventriculus, it is lined by a chiti- 

 nous coat continuous with the chitinous layer of the integu- 

 ment, and beset for the greater part of its extent with fine 

 setiform processes. Beneath this is the proper endoderm, 

 consisting of a layer of cells. Next follows a structureless 

 membrana propria or basement membrane ; and this is suc- 

 ceeded by two layers of striped muscular fibres, the internal 

 disposed longitudinally and the external circularly. In the 

 proventriculus, the muscular layers become much thicker, and 

 some of those of the outer layer acquire a radial arrangement, 

 while the longitudinal muscles are disposed in bundles which 

 correspond with the six principal ridges. In the chylific ven- 

 tricle, the muscular layers and the basement membrane are 

 disposed much as before. The basement membrane presents 

 pits on its free surface in which rounded cells are lodged, and 

 is beset between these by the elongated cells of a cylinder 

 epithelium. The free ends of these present a thick wall, 

 marked by vertical striations. There is no chitinous layer. 

 The caeca are merely diverticula of the wall of the chylific 

 ventricle. 



The intestine, finally, repeats the structure found in that 

 part of the alimentary canal which lies in front of the chy- 

 lific ventricle and is provided with a setose chitinous lining. 



Basch found the secretion of the salivary glands and the 

 contents of the crop acid, 2 and that an infusion of the sali- 

 vary glands, acidulated with hydrochloric acid, digested fibrin. 

 The contents of the chylific ventricle were neutral or alka- 

 line ; and an infusion of the chylific ventricle at once turned 

 starch into sugar. The same effect was produced by an infu- 

 sion of the salivary glands. 



The heart (Fig. 98, h) is a slender inconspicuous tube, 

 which occupies the middle line of the dorsal wall of the 

 abdomen, and presents, at intervals, pairs of lateral apertures. 

 The wall of the abdomen internal to the chitinous integu- 

 ment is lined by a soft cellular substance (hypo dermis), the 

 outer layer of which represents the ectoderm or epidermis, 

 while the deeper part is the parietal layer of the mesoderm. 

 This last contains a stratum of longitudinal muscular fibres, 

 divided into segments or myotomes, in correspondence with 

 the somites, and numerous tracheae. The heart is inclosed in 



1 a Sitzuns:sberichte der Wiener Akademie," xxxiii., 1858. 



2 Plateau denies that the salivary secretion of Blatta is ever acid, and as- 

 cribes the occasional acidity of the contents of the crop to the food. 



