ox I2^SECT ANATOMY. 405 



arise from its internal surface and pass forward to the mandibles. 

 The only really cerebral organs are the ganglion masses of the 

 supra-oesophageal ganglion, which correspond with the corpora 

 quadrigemina of the vertebrate brain, and the ganglia of 

 sympathetic and vagus nerves. The vertical cross section, which 

 the drawings represent as made immediately through the vertex 

 of the head, shows the internal processes already mentioned, 

 and, as seen in this section, they show how the cranial cavity is 

 partitioned off, leaving special chambers (orbital, antennal) on each 

 side, -whilst in the longitudinal section the separation of oranial 

 cavity from the face is seen to be effected by the same processes. 



The central slice, obtained by a vertical cross section of the head, 

 commencing from the top in front of the antennae and carried down 

 to the throat, and another parallel section made behind the antennae 

 and slicing with it the anterior portion of the cornea on each side, 

 is a most important section. This central slice (about -jL to -^^ in. 

 thick) contains the whole brain with sympathetic and vagus ganglia, 

 together with aesophagus and its salivary glands. I^Text in impor- 

 tance are horizontal sections from the occiput to the top of the nose. 

 Looking towards the base, we see, as in the drawings and prepar- 

 ations, the symmetrical disposition of muscles, running on each side 

 from the inner surface of the cranial cavitj^ to the mandibles and 

 maxillae, with the central position of the aesophagus and the infra- 

 aesophageal ganglion in front of it, also the tongue and the muscles 

 connecting it with the anterior edges of the ascending internal 

 processes, and the maxillary muscles on each side, with the maxillae 

 and all the parts of the lower jaw. And looking upon the surface 

 of the section of the upper half of the cranium we see, as in the drawing, 

 the symmetrical disposition of the orbital and antennal chambers 

 and the optic ganglia on each side, the vault of the fauces and 

 palate, and the inner surface of the labrum, &c. 



As the descriptive anatomy of the head of the cricket will occupy 

 a whole evening, the present rough sketch is intended merely to 

 describe in a general way, the drawings before us, and so to 

 enable those who examine the preparations on the table to under- 



