EXAMINATION OF TISSUES FOR PARASITES 725 



melting point of paraffin at the hottest end. Some odd pieces of section, 

 not required, and not necessarily containing any tissue, are then taken, 

 and placed on a slide with a small drop of water. A large drop of 

 water is then placed on the heated copper, and the trial sections on 

 their slide are lowered on to it. If the copper is too hot, they will 

 melt, and another trial must be made at a point further away from 

 the flame. A place is soon found where the sections at once straighten 

 out to their full extent without melting. The slides full of sections are 

 now placed on this point one by one, care being taken that there 

 is always a film of water between the copper and the glass, and a 

 sufficiency of water on the slide. The sections straighten out in a 

 second or two, and should at once be removed. In doing this always 

 tilt up the end of the slide which is on the copper first, and not the end 

 which is in the fingers, or the sections may flow from the slide to the 

 copper. Remove the superfluous water with a pipette or filter paper, and 

 leave the slides to dry overnight. 



In dealing with serial sections a great deal of time and trouble can be 

 saved by mounting a large number of sections on the same slide. The 

 upper and lower edges of the block should be trimmed very carefully in 

 order to get a straight ribbon, and this should be laid out on large sheets 

 of paper till the whole has been cut. A piece of card is then taken and 

 cut to a size two-thirds the length of the coverslips which are to be used 

 for mounting. Using this as a measure, cut up the ribbon into lengths, 

 with due care lest the order in which they lie should be disturbed. The 

 cut should be made with a sharp knife with a thin and perfectly clean 

 blade, otherwise the sections will adhere to it. Now take a camel's hair 

 brush, moisten the tip slightly, and apply it to one end of one of the 

 pieces. It will adhere, and the row of sections may be lifted up and laid 

 on the slide, near one edge. Then take the next row, and lay it parallel 

 with the first, and so on till the slide is filled as full as it will hold, 

 each row of sections touching its neighbour. The first section should be 

 placed at the left hand side of the slide, at the point which will 

 correspond with the left hand top corner of the label ; the first section of 

 the second row is next to the first of the first row, and so on. 

 In this way a hundred or more sections can be mounted on a single 

 slide. The particular order does not matter, so long as the worker 

 adopts a uniform one for all his sections. 



The examination of insect tissues for parasites, either natural parasites 

 or pathogenic haematozoa, should be carried out in a methodical manner. 

 There is a right and a wrong way of doing it, and as the tissues are 



