LABORATORY METHODS IN MALARIA 377 



cent solution of sodium thiosulphate has been added. They are 

 finally brought into pure seventy per cent ethyl alcohol. It is well 

 to allow abundant time for washing, two hours at least. 



Material may be preserved in the seventy per cent alcohol or 

 stained at once. All the processes of staining, dehydrating and 

 clearing may be carried out in vials or watch glasses. 



Salivary glands or stomachs may be stuck to the slide by the 

 fixative and subsequently treated as one would a section. Schau- 

 dinn's fixative will usually fasten specimens, at least the well flat- 

 tened ones, to the slide if the following precautions are taken: 

 Draw away the salt solution with a piece of filter paper until the 

 specimen is almost dry. Add the fixative very gradually at first, 

 so that fixation takes place while the object is in close contact 

 with the slide. A drop of fixative may be put on the slide near the 

 specimen and gradually drawn to it with a needle. In the case of 

 stomachs, remove the terminal segments of the abdomen or dissect 

 them out so that they will adhere well. The more material in con- 

 tact with the slide, of course, the more likely the specimen is to 

 adhere. After a few minutes of fixation transfer the slide to fresh 

 Schaudinn fixative in a Coplin jar. Specimens are eventually 

 washed, stained, dehydrated and cleared in Coplin jars or similar 

 containers. 



In case one wishes to demonstrate the position of oocysts on 

 the rounded wall of the stomach or to obtain material for section- 

 ing, it is best to avoid too much flattening. A stomach may be 

 examined for oocysts without the coverglass. However, a stomach 

 taken from a freshly killed insect will usually resume the rounded 

 form after the coverglass is removed, provided it has not been 

 flattened too much. Add new salt solution after the removal of the 

 coverglass. A flattened stomach may be made to resume its 

 rounded shape if the slide be gently heated while the stomach is 

 submerged in liquid (MacGregor). 



Stomachs or salivary glands may be fixed, washed, stained, de- 

 hydrated, cleared and mounted in balsam without removing the 

 coverglass. Use a small, thin coverglass not over six millimeters 

 in shortest dimension. A narrow rectangular cover is preferred. 

 Draw away the surplus salt solution. Run the Schaudinn or other 

 fixative under the cover, and "irrigate" by withdrawing the fixa- 

 tive from one margin of the cover with filter paper while supply- 

 ing new fixative at the other. The coverglass should be kept under 



