THE EXAMINATION OE WATER 



639 



Remove wings at right angles to the body and mount likewise. 



Transfix the thorax with a fine needle and remove the head by pull- 

 ing it away from and backwards off the thorax; in this way the salivary 

 glands may be withdrawn from the thorax, and they can be examined 

 under the microscope for parasites. 



Then take the remainder, bruise the abdomen across the last seg- 

 ment, and draw it away with another needle; in this way the internal 

 viscera will be dra^^■n out also, and if one is fortunate the salivary 

 glands, if not already removed, will be withdrawn. 



The stomach, rectal glands, spermathecae, &c., will be well shown. 



Examine the gastric contents for malarial parasites. 



If the salivary glands are not removed, tease the thorax into very 

 small portions in a drop of saline and examine. There is much debris 

 resulting from this method, and the glands may be lost. 



Stomach of mosquito showing malarial parasites. 



The parts not being examined should be kept in saline, or better, 

 liquor potasscu in a watch-glass. 



Press the proboscis out under a cover slip and examine; several of 

 the elements may be seen in each specimen thus treated. Examine 

 the base of the proboscis and the thoracic muscle for filarial embryos. 



THE EXAMIXATIOX OF WATER. 



Good waters are spring, deep well, and upland service waters. 

 Suspicious waters are stored rain and surface water from cultivated 

 land. 



Dangerous waters are shallo\\- well and river water to which sewage 



has access. 



There are four examinations : — 



Biological, Phvsical, Bacterial, Chemical. 



