CH. IX] LABELING AND STORING PREPARATIONS 261 



\ 362. Isolation of Muscular Fibers.— For this trie formal dissociator may 

 be used (I 358), but the nitric acid method is more successful ($ 420). The 

 fresh muscle is placed in this in- a glass vessel. At the ordinary temperature 

 of a sitting room (20 degrees centigrade) the connective tissue will be so far 

 gelatinized in from one to three days that it is easy to separate the fascicles 

 and fibers either with needles or by shaking in a test tube or shell vial (Fig. 

 205) with water. It takes longer for some muscles to dissociate than others, 

 «ven at the same temperature, so one must try occasionally to see if the action 

 is sufficient. "When it is, the acid is poured off and the muscles washed gently 

 with water to remove the acid. If one is ready to make the preparations at 

 ■once they may be isolated and mounted in water. If it is desired to keep the 

 specimen indefinitely or several days, the water should be poured off and 2% 

 formaldehyde added. The specimens may be mounted in glycerin, glycerin 

 jelly or balsam. Glycerin jelly is the most satisfactory, however. 



ARRANGING AND MOUNTING MINUTE OBJECTS 



I 363. Minute obj ects like diatoms or the scales of insects may be arranged 

 in geometrical figures or in some fanciful way, either for ornament or more 

 satisfactory study. To do this the cover-glass is placed over the guide. This 

 guide for geometrical figures may be a net-micrometer or a series of concentric 

 circles. In order that the objects may remain in place, however, they must be 

 fastened to the cover-glass. As an adhesive substance, mucilage or liquid 

 gelatin (§ 415) thinned with an equal volume of 50% acetic acid answers well. 

 A very thin coating of this is spread on the cover with a needle, or in some 

 other way and allowed to dry. The objects are then placed on the gelatinized 

 •side of the cover and carefully got into position with a mechanical finger, made 

 by fastening a caf's whisker in a needle holder. For most of these objects a 

 simple microscope with stand (Figs. 149, 164) will be found of great advantage. 

 After the objects are arranged, one breathes very gently on the cover-glass to 

 soften the mucilage or gelatin. It is then allowed to dry and if a suitable 

 amount of gelatin has been used, and it has been properly moistened, the objects 

 will be found firmly anchored. In mounting one may use Canada balsam or 

 mount dry on a cell (J 343, 353). See Newcomer, Amer. Micr. Soc.'s Proc, 

 1886, p. u8; see also E. H. Griffith and H. L. Smith, Amer. Jour, of Micros., 

 iv, 102, v, 87; Amer. Monthly Micr. Jour., i, 66. 107, 113. Cunningham, The 

 Microscope, viii, 188S, p. 237. 



LABELING, CATALOGING AND STORING MICROSCOPIC 

 PREPARATIONS 



I 364. Every person possessing a microscopic preparation is interested 

 in its proper management ; but it is especially to the teacher and investigator 

 that the labeling, cataloging and storing of microscopic preparations are of 

 importance. "To the investigator, his specimens are the most precious of his 

 possessions, for they contain the facts which he tries to interpret, and they 



