COLLECTING, PRESERVING .AND APPLIANCES 37 



is required. This is filled with a sample of the paraffin 

 which is selected for use, and is then placed near the middle 

 of the copper plate, not across, but parallel with the length 

 of the plate. If the lamp be now lighted and placed under 

 one of the projecting ends of the plate, its heat is conducted 

 by the copper to the narrow tray, and it will be found that 

 a greater or less proportion of its length will become melted. 

 At the point where the melted and solid portions meet it is 

 clear that the paraffin is just at its melting point, and 

 opposite this point are placed the small capsules of paraffin 

 in w^iich the structures for imbedding are to be placed. 

 The long narrow tray, in fact, acts as a thermometer, and if 

 the plate be allowed to reach, so to say, a settled condition 

 before placing the capsules of tissues on it, it will be found 

 that the heat of the lamp is quite uniform enough to render 

 little or no close supervision necessary, and that in a still 

 atmosphere it may often be left for hours without touching. 

 I do not, of course, propose such an appliance as a substitute 

 for the self-regalating one where gas is available, but where, 

 as in most tropical countries, there is no gas supply, it will 

 be found to be something more than an inefficient make- 

 shift, and with a small amount of occasional attention will 

 yield as good results as can be desired. 



With the exception of the wings, which are best mounted 

 dry, the cover bemg merely secured by a perforated label, 

 parts of Mosquitoes are best mounted in balsam, after pass- 

 ing through absolute alcohol and clove oil. 



The subject of the methods of determining the relation 

 of Mosquitoes to blood parasites is rather outside the scope 

 of a book like the present, but a few words on the subject 

 may not be out of place. To infect a Mosquito all that is 

 necessary is to introduce a few of the species under investi- 

 gation under a Mosquito netting, beneath which the patient 

 harbouring the haematozoa is to sleep. The insects should 

 be females, and to avoid the possible fallacy of their having 

 been previously infected, it is better, if possible, to employ 

 for the purpose only insects that have been reared in 

 captivity from larva?. Although a certain number of con- 

 firmatory experiments of the infection of the vertebrate host 



