PLATE XXIII 



Figure 1. The alimentary tract of Culex, dissected out without 

 traction, l.d., lateral diverticulum. cd., cardia. st., 

 stomach ' : the cardia and the stomach make up the 

 mid-gut. Other letters as before, x 80. 



Figure 2. Cells from the mid-gut of Culex. Note the internal 

 layer, and the vacuoles. n., nuclei lying between the 

 bases of the columnar cells. These belong to small 

 cells which will eventually replace the columnar ones 

 when desquamated, x 800. 



Figure 3. The mid-gut of Culex when distended with blood. 

 The amount of distension may be judged by compar- 

 ing the relative size of the oesophagus in this figure 

 and in figure 1. x 30. 



Figure 4. The shape of the mid-gut when dissected out by the 

 ordinary method, involving traction. 



Figure 5. Schematic longitudinal section through the commence- 

 ment of the mid-gut, s.a., opening of the diverticula. 

 m.c., sphincter muscle separating the fore-gut and 

 the mid-gut, c., chitinous intima. st., striated border 

 (Stabchenschaum). m., external muscular fibres, 

 ep., epithelium. After Schaudinn. 



