g6 NORMAL HISTOLOGY. 



tion, since here the muscle-cells are unusually large. A 

 segment having been distended as above with Miiller's 

 fluid, it should be immersed for ten days in the same, 

 then carefully washed and put for a day or two in strong 

 alcohol. A bit is then cut out, imbedded in celloidin, 

 and thin sections made in a direction exactly at right 

 angles to the axis of the gut. The sections are stained 

 double and mounted in balsam or glycerin. In such 

 a preparation two layers of muscle-cells are seen : in one 

 the cells are seen in transverse, in the other in longitu- 

 dinal section. Since the cells lap over one another, in 

 the transverse sections the forms which they present will 

 obviously differ, depending upon whether they have been 

 cut across at the level of the nucleus, or at a point nearer 

 the extremity. In such a preparation, the cementing 

 substance between these cells may be seen in the trans- 

 verse sections ; and the serosa and mucous membrane 

 are seen on opposite sides of the muscular layers. 



Muscle-cells of Frog's Bladder. Instructive pictures 

 of very much elongated, slender muscle-cells, lying 

 singly or arranged in narrow interlacing fascicles, may 

 be obtained from the frog's bladder by the following 

 method : the spinal cord of a frog being broken up, the 

 abdominal cavity is largely opened by a crucial incision, 

 and a curved canula, attached to a small syringe filled 

 with a saturated solution of bichromate of potassium, is 

 passed into the cloaca and directed forward into the 

 bladder. The fluid is now slowly injected, and when the 

 bladder is partially distended a ligature is thrown around 

 its base, and the injection continued till the organ is 

 fully distended. The ligature is now drawn tight and 



