no 



preparation, and is all important in relation to 

 malarial studies. 



The following appearances are seen in a good 

 preparation : — 



1. Well-defined tubes with spiral lining (air 

 tubes or tracheae). Note that these branch and 

 ramify upon the surface of the mid- gut and mal- 

 pighian tubes (Fig. 31). 



2. Large muscular fibres, together with 

 elastic fibres, forming a check pattern. Note that 

 they are circular and longitudinal (external). 

 Note that at the edge of the viscus they are seen 

 in optical section (Fig. 31). 



3. Large cells with large nuclei and granular 

 protoplasm (epithelium of mid-gut). Note some 

 in situ forming a single layer of polygonal epi- 

 thelium, and others detached and in process of 

 being carried along by fluid streaming from interior 

 of mid-gut. Note that in some places these cells 

 are undergoing vacuolization with dancing of the 

 protoplasm granules (Fig. 31). 



4. Note any contents of the stomach — 



(i) Remains of blood. 

 (ii) Crystals of various kinds. 

 (iii) Gregarines, flagellates, bacteria, etc. 



5. Note that in focussing downwards one 

 passes through a double thickness of wall. Note- 

 that the air tubes are focussed on the upper and 

 lower surfaces of the preparation, and the epithe- 

 lium and crystals in the middle. 



6. Trace several of the finer air tubes to 

 their apparent termination, and note that when 

 they lose their spiral lining they are continued as 

 very fine transparent tubules (air capillaries). 



