1896 THE MICROSCOPE. 87 



PRACTICAL SUGGESTIONS. 



By L. a. WILLSON, 

 ci<e;vei.and, ohio. 



Crystals from Blood. — It is interesting- and frequently 

 of pathological importance to examine crystals in blood. 



Crystals in blood are most readily formed, if a drop of 

 blood be enclosed beneath a thin cover g-lass, allowed nearly 

 to dry, and a small quantity of water be added. 



To obtain haemin crystals, place blood on slide and add 

 a drop of water containing- a trace of salt ; apply a thin 

 g-lass; allow a little g-lacial acetic acid to flow in and mix 

 with the blood. Then apply heat until the mixture almost 

 boils. Examine the resulting- crystals with a one fourth 

 or one fifth objective. The haemog-lobin crystals differ in 

 shape in the various mammals. They are always of mi- 

 croscopic size and of a brig-ht red color. 



In man and most mammals they are of the shape of pris- 

 matic needles, or rhombic plates. 



Melicerta Ringens. — This beautiful animal maybe found 

 both in fresh and stag-nant water. A fine picture of this 

 specimen may be seen in Dalling-er's Carpenter, 7th ed., 

 Plate XV, fig-. 3. They are attached to roots and stems in 

 the w^ater. Their presence may be detected by the un- 

 assisted eye. They are generally in colonies. They are 

 attached by a foot which is prolonged into a pedical. They 

 build for themselves a sheath, or carapace of pellets which 

 they secrete. This sheath is their permanent home. 

 When broken they repair the damag-e. When alarmed 

 they retreat into the sheath. When all is quiet, they pro- 

 tude from the sheath, unfold their arms and vig-orously 

 revolve their cilia. To the eye the sheath appears very 

 dark brown, or nearly black. Under the microscope they 

 are of anorang-e brown color. To examine, place the twig- 

 or rootlet containing- them in a shallow cell and cover. 

 They may be nicely seen with a one inch objective, but for 

 finer details a hig-her power may be used. In collecting- — 

 gather the roots and stems from the water and place in a 



