127 



Mosquito tissues are so delicate tliat in 

 mounting it is difficult to avoid the separation of 

 portions or the whole of the section. This is 

 especially so in the case of the chitin, which 

 frequently breaks away. 



Obreggia's method is recommended as giving 

 excellent results : — 



1. A slide is smeared with a thin film of a 

 mixture, consisting of two parts of commercial 

 liquid glucose and one part of a solution of 

 dextrin (dextrin, i6 oz. ; water, 17^ oz. ; thymol, 

 15 grains). 



2. Place the sections directly on this layer 

 on the slides. 



3. Heat at 40° C. for some hours until the 

 glucose becomes hard. 



4. Dissolve off the paraffin in xylol and pass 

 through absolute alcohol. If the alcohol is not 

 quite absolute, the glucose will dissolve and the 

 film come off. 



5- Dry- 



6. Pour on thin film of photoxylin, and 



allow to dry until edges of film become slightly 

 crumpled. 



7. Put slide in water. Sections come away 

 in the film of photoxylin. 



8. Stain in situ, dehydrate and clear in 

 carbol xylol (xylol, 3 parts ; absolute phenol, 

 I part). Mount in balsam. 



To Stain. — The best stain for general use in 

 sections is haematein (vide p. 50). 



The Examination of Separate Organs 



Remove the mid- gut or the ovaries or other 

 organs desired, and place in a saturated solution 



