(3) Glycerine, vide p. [472].
Staining.—In case of quite small Nematodes, e.g., Anguillulidæ, carmine may be used, but as a rule staining is not advantageous.
Rolling.—In order to study the mouth parts, or bursa, etc., it is necessary to place the worm in any desired position. This is done as one would roll a penholder along the table by one’s finger placed on top of it. In the case of a worm, one edge of the cover-glass is placed over the worm, the other is supported by a strip of cardboard. By tapping the cover-glass the worm will now revolve as much as required provided it is round and straight. In certain cases it may be necessary for this purpose to cut off the head or tail. Roll these separately.
When a suitable position is got, the worm may be fixed in this position by pressure on the cover-glass, so as slightly to flatten it.
Mounting the Head.—If it is required to get an end view, it is necessary to cut off the head transversely as near the end as possible, and then mount.
Detection of Eggs (Bass and Hall).—Mix the fæces thoroughly with ten times the volume of water. Filter through gauze. Centrifugalize the filtrate. Wash the sediment and centrifugalize. Repeat twice. To sediment add CaCl2 solution, sp. gr. 1250. The eggs float to surface. Pour off surface fluid. Dilute to sp. gr. 1050. Centrifugalize. Examine sediment, which contains practically all the eggs in the stool.
Detection of Small Nematodes.—Mix the fæces thoroughly with water. Allow to settle for five minutes. Carefully decant off, or better, syphon off the fluid. Mix the sediment again with water. Allow to settle. Remove the fluid. Repeat several times. Examine the sediment in a Petri dish. As the fluid is poured off, the worms will be seen collected in the backwater. Remove them with a brush. Fix in hot 70 per cent. alcohol.
Cultivation of Larval Forms of Ancylostoma and Strongyloides.
A modification of the second method of Looss (p. [455]) is that of Fülleborn. A glass filter funnel is lined with linen or with cotton wool dyed black with iron-tannin. On this is placed a layer of sterile sand, and on top of this the fæces. The whole is moistened. The larvæ hatch out and wander through the meshes of the wool, appearing on the edges of the same as white threads visible to the naked eye. With a platinum needle these can be easily removed. The glass filter can be placed on a glass cylinder, and this in another large stoppered cylinder containing caustic potash solution at the bottom, so that any larvæ escaping from the funnel are killed.