THE (ESOPHAGUS, STOMACHS AND INTESTINES. 49 



numerous small vessels, which apparently perforate the quasi- 

 cartilaginous tissue of the plug, which thus affords a rare 

 exception to the rule that the tracheae do not penetrate into 

 the substance of the organs which they supply. 



Functions of the Proventriculus. Many opinions have been 

 held with regard to the functions of the proventriculus. It is 

 undoubtedly homologous with the gizzard of manducatory 

 insects, and it may serve for crushing soft, semi-fluid food. 

 Weismann asks if it may not be regarded as glandular, but 

 such a view is in no way suggested by its structure. More 

 recently Emery has ascribed a suctorial function to the pro- 

 ventriculus in Ants (Formicidas) [169], which closely resembles 

 that of the Diptera. The arrangement of the plug, which 

 resembles the plunger of a pump, lends some support to this 

 view; but, on the whole, I am inclined to think it is a gizzard 

 and nothing more. 



The Proventricular Ganglion differs but little from the same 

 structure in the larva. It consists of large ganglion cells, and 

 lies in front of the proventricular oesophagus. It gives off 

 numerous nerves to the chyle stomach, proventriculus, and 

 oesophagus. 



The Chyle Stomach commences in front above the proventri- 

 culus, traverses the thorax, enters the abdomen beneath the 

 mesophragma, and curves upwards and backwards in the 

 middle line ; at the posterior margin of the second abdominal 

 segment it deviates to the right, and after a short course 

 terminates in a narrow pylorus, which enters the proximal 

 intestine. 



The thoracic portion is covered by small hemispherical 

 projections, except at its anterior extremity, which is smooth 

 like the abdominal portion. Hence the chyle stomach may be 

 said to consist of three parts or segments : the caput, the 

 thoracic or intermediate part, and the pyloric extremity or 

 abdominal part. The muscular coat of the caput and the 

 pyloric parts of the organ is continuous ; but in the interme- 

 diate portion its external longitudinal coat is arranged in six 

 longitudinal bands, whilst the circular fibres are arranged in 



