XII] CILIATED CELLS. MUSCLE CELLS 97 



into a considerable excess of 50 p.c. acetic acid, and after a few 

 minutes washing with water, they may be stained in picro- 

 carmine or other carmine fluid and mounted in glycerine or in 

 Farrant's solution. The separation of the cells from the several 

 fluids is best done by a small centrifugal machine. 



This method is only good for observing the shape of the cells. 

 The nucleus and the sarcoplasm of the cells are better seen by 

 the following method. A small strip of muscular tissue is 

 stretched and placed in 1 p.c. potassium bichromate or in 30 p.c. 

 alcohol for 2 to 3 days, washed with water, stained with eg. 

 picrocarmine by irrigation under the cover-slip and mounted in 

 dilute glycerine. The isolation of the cells is however not very 

 good. 



Ordinarily it is best to distend the tissue with the isolating 

 agent, when this can be done, as in the case of the bladder and 

 intestine. After leaving in this for one day, it may be cut open 

 and left in an aqueous and dilute alcoholic stain for one or two 

 days before teasing. 



When it is desired to isolate a few muscle cells imbedded in 

 much connective tissue the following method may be employed. 

 A small piece of the tissue is placed in 15 to 20 p.c. nitric acid 

 for a day, it is then slightly teased, and shaken up well in a test- 

 tube with water, centrifugalized, and the residue examined. 



Longitudinal fibrillation. This is much more distinct in 

 invertebrate than in vertebrate unstriated muscle ; for vertebrate 

 muscle Ranvier recommends the intestine of the frog (distended 

 with 30 p.c. alcohol for one or two days, and a strip of muscular 

 coat teased). Engelmann recommends the fresh stomach wall of 

 the frog treated as follows : a section of the muscular coat at 

 right angles to the circular fibres is made with a Valentine's 

 knife, it is mounted in 10 p.c. NaCl and examined at once. 

 Faint dots indicating fibrillse may be seen in the transverse 

 sections of the muscle cells. 



Double oblique fibrillation. According to Schwalbe this is 



seen best in Solen, well also in the oyster and fresh -water mussel. 



In anodon cut through the attachments of the posterior 



