1890.] MICEOSCOPICAL JOURKAL. 151 



striated or skeletal muscle and smooth or unstriated muscular tissue. 

 For the cardiac muscular tissue, caustic potash is greatly superior. 



2. As just stated, a 20 per cent, solution of nitric acid has been found 

 the best isolating agent for the fibres of striated muscle. Perfectly 

 fresh tissues are preferable, and in fact necessary for obtaining the best 

 results, especially in separating the fibres their whole length. If the 

 tissue is not fresh the fibres become fragile and cannot be isolated 

 throughout their whole extent. 



3. In order that the fibres may remain straight, the muscle should be 

 suspended in the acid with its natiual attachments if possible. When 

 that is impracticable the muscle should be extended on a piece of cork 

 and pinned in position with vaselined pins. The vaseline prevents the 

 corrosion of the pins. 



4. If the object is to isolate fibres throughout their whole length, the 

 fat and connective tissue on the surface should be removed either before 

 the immersion in the acid or as soon as the acid has sufficiently softened 

 the connective tissue so that it may be removed without too much drag- 

 ging upon the specimen. When the fibres can be separated easily the 

 action is sufiicient. The time varies according to the temperature. 

 At the ordinary temperature of a living room, from one to three days is 

 sufficient for almost any muscle. If the connective tissue is very dense 

 the time may be increased. By using heat the action may be completed 

 in a few minutes, but it is not so satisfactory, as the surface la vers are 

 too much, and the interior laj'ers tooJittle, afl'ected. 



5. When the action is sufiicient the muscle is transferred to water to 

 remove the acid. It is well to change the water several times. 



6. If it is desued to study the fibres with reference to their form, length, 

 and relations, the manipulation should be as little as possible. A fas- 

 cicle is chosen which frays easily with a coarse sewing needle. It is 

 transferred to a slide with a drop of water, or if a yellow color is de- 

 sired, a drop of glycerine tinged with picric acid. The fibres are then 

 carefully separated with coarse needles under a dissecting microscope. 

 The excess of glycerine is removed with blotting paper, and a drop of 

 warm glycerine jelly is allowed to spread slowly over the preparation. 

 The fibres are arranged with needles and the slide allowed to cool until 

 the glycerine jelly has a glutinous consistency. It is then covered with 

 a v^arm cover. The partly-cooled glycerine jelly prevents the fibres 

 from becoming entangled when the cover is put on. 



7. If the nuclei are to be especially studied, the muscle remains in 

 water until all the acid is removed. Then it is stained in Koch's tuber- 

 cle stain, diluted four or five times w^ith water, for twelve hours or 

 more. A fascicle is then removed to a slide with 20 per cent, alcohol, 

 containing sufficient picric acid to make it a lemon-yellow color. This 

 is gradually replaced by 50 per cent., and then by 95 per cent, alcohol. 

 In the last the fibres are separated as described above, and after draining 

 away the alcohol, clove oil collodion is added and the fibres finally ar- 

 ranged. As soon as sufiicient evaporation has taken place to fix tlie fibres, 

 a cover-glass is coated with Canada balsam and placed upon the speci- 

 men. If the result is successful the nuclei are stained a brilliant red 

 and the body of the fibre yellow. The transverse striai are always very 

 sharp and clearly defined after picric acid staining. 



S. If it is not convenient to study the specimen at once, or if it is a 



