374 RESEARCH IN PROTOZOOLOGY 



drop of balsam, which is placed on a dry part of the slide. The 

 balsam holds the coverglass firmly in position. The whole prepa- 

 ration is then dried, fixed with methyl alcohol, and stained with 

 Giemsa as one would a thick blood-film. Or, one may stain by 

 Wright's or any thin-film method. All or the most of the sporo- 

 zoites remain on the slide or the cover. 



When mosquitoes caught in the wild state are examined to de- 

 termine the percentage infected with sporozoites, a saving of time 

 in dissection is very desirable, since the percentage infected is 

 usually very small, and large numbers have to be examined in 

 order to obtain significant figures. Some workers (Sergent, E. 

 and E., 1912) dissect out on a slide the contents of that portion 

 of the thorax in which the salivary glands lie, dry the material, 

 fix with methyl alcohol and stain with Giemsa. Smears from many 

 mosquitoes can be made on a single slide and may be stained and 

 examined at leisure. 



I have had practically no experience with this method. It seems 

 to be a good one for detecting at least the minimum percentage of 

 infections, for it is very probable that sporozoites, if present in 

 large numbers, would be found in preparations made in this way. 

 It would appear desirable that the salivary glands, or at least por- 

 tions of them, should appear in negatives as evidence that the dis- 

 sections were properly made. 



Permanent preparations of stomachs or salivary glands. The 

 preparation of material for cytological or other detailed study of 

 mosquito material demands special methods which cannot always 

 be attempted in ordinary mosquito infection experiments. But it 

 is often desirable to preserve material sufficiently well for class 

 or other demonstration purposes, and a few directions for making 

 permanent preparations are given. It is presumed that the reader 

 is familiar with the ordinary technique of preparing tissues, in 

 sections or bulk, for microscopic examination, or has access to 

 one of the numerous manuals which describe such methods. 



Unstained specimens of stomachs and of salivary glands may 

 be mounted in dilute formalin under sealed coverglasses. A special 

 preserving fluid is recommended by MacGregor: 



5% solution of borax 10.00 cc. 



40% solution of formaldehyde 10.00 cc. 



Glycerin 0.25 cc. 



Water to make up 100.00 cc. 



