240 THE MICROSCOPE. 
cent. ammonium chromate for a day; remove to water for half an 
hour; stain with picro-carmine or hematoxylin, and mount in 
glycerin. Cells which divide at their ends may be seen in the (e. g.) 
urinary bladder of a frog. 
OsLiquELy SrriateD Muscre.—Cut through both attachments of 
the posterior adductor muscles of an anodon; place the posterior 
yellowish part in 33 per cent. alcohol for a day. A small strip 
should also be examined fresh. The angle between the crossing 
fibrille is greater in the yellow part of this muscle than in the white 
dorsal part. A few fibers should be torn off and examined straight- 
way in the blood of the animal, or in .75 per cent. salt solution. To 
isolate the fibers and to bring out more distinctly the fibrille, the 
muscle should be placed in 30 per cent. alcohol or 1 per cent. 
potassium bichromate for one or two days, and a small piece teased 
out in the isolating fluid. To obtain the fibers in the extended state, 
a wedge should be forced between the shells, and the whole animal 
then: placed in the reagent. To obtain the fibers contracted, it is 
sufficient to cut away the muscle from its attachments. Similar 
muscular- tissue is present in many other invertebrates. It occurs, 
for instance, in the skin muscles of Lumbricus terrestris, and in the 
foot muscle of Helix pomatia. 
STRIATED MUSCULAR FIBERS. 
Livinc Frsers.—These muscles may be pinned out whole over 
a ring of cork. The mylohyoid of the frog and the subcutaneous 
muscles of the face and neck of the rabbit may be so treated. With 
thick muscles a few fibres should be torn out and mounted in 
aqueous humor or freshserum. The fibers of insects are best mounted 
in the blood of the animal. According to Nasse, a 1—1.5 per cent. 
salt solution is better than a6 per cent. for certain muscular fibers 
(e. g., flies). In some fibers contraction waves may be seen; as the 
fibers die, one part of the fiber may be seen to be contracted, and 
the contraction to spread from this spot towards the end of the 
fibers. The behaviour of the various bands should then be care- 
fully noted. 
Mouscie Treated with Reacents.—To observe the various bands 
the muscle should be stretched before being placed in the reagent. 
This may be done conveniently by cutting out the parts to which the 
muscle is attached, and pinning out the attachments of the muscle 
over aring of.cork. The most generally useful reagents are abso- 
lute alcohol, osmic acid, 0.5 per cent. for about five minutes, then 
alcohol; a concentrated aqueous solution of salicylic acid (this, like 
