PARASITOLOGY. 221 
If alcohol be used then the parasite should be 
placed in a 25% solution for one week. Then a 50% 
solution for one week. Then a 75% solution for one 
week. Then absolute. Alcohol has a tendency to 
shrivel the tissues of round worms. Formalin has a 
tendency to expand or swell the tissues, hence some 
worms, as the Stephanurus Dentatus, havea tendency 
torupture at the genital or anal openings, if too 
strong a solution be used. 
For museum purposes the smaller specimens can 
be placed between two glass slides held together 
with silk thread tied together at each end and placed 
in an upright position in the fluid. The back slide 
should be covered with black shellac and allowed to 
dry before being used. 
TO STAIN AND MOUNT ENTOZOA. 
When coilecting worms for laboratory study they 
should be immediately placed in the following solu- 
tion: 
50 parts of 70% alcohol. 
50 parts aqueous solution bichloride of mercury. 
A few drops acetic acid. 
The parasite thus killed and preserved should then 
be washed ina gentle stream of water for several 
hours. Then place in 25% alcohol for twenty-four 
hours; then absolute. The parasites stain with 
either alcoholic eosin or picric acid stains; hema- 
toxylin or methylene blue can be used for secondary 
stainif desired. After staining the desired shade (the 
time of which varies with the species of worm) the 
specimen should be clarified in xylol, oil cedar or 
