MOSKOWITZ 



214 



MOUNTING MEDIA 



dry again. Cover with mixture of 

 acetic acid, 1 cc; 40% formalin (com- 

 mercial formaldehyde), 2 cc; aq. dest., 

 100 cc. Rinse well in aq. dest. and heat 

 till steam rises in mixture of carbolic 

 acid, 1 cc; tannin, 50 gm.; aq. dest., 

 100 cc Rinse in aq. dest. j min. and 

 heat slightly 1-2 min. till smear becomes 

 brown or slightly black in silver solu- 

 tion made up as follows: To 20 cc. aq. 

 dest. add "platinum loop" of 25% am- 

 monia and then drop by drop from 

 pipette of 10% aq. silver nitrate until 

 an opalescent ppt. appears. About 

 0.5 cc. of silver solution will be needed. 

 After silvering smear rinse well in aq. 

 dest., mount and seal edges with 

 paraffin. 



Moskowitz, see Protein Silver for Staining 

 Protozoa. 



Mosquito larvae, technique of raising anoph- 

 eline (Bates, M., Am. J. Trop. Med., 

 1941, 21, 103-122). Bodian technique 

 for mosquito nervous system (Rogoff, 

 W. M., Stain Techn., 1946, 21, 59-61). 



Motion Pictures. The technique of making 

 motion pictures of living cells and or- 

 gans has proved its worth. The movies 

 can be projected again and again and 

 the sequence of events made very clear. 

 It is important to remember that mo- 

 tile cells do not run around at the speed 

 indicated, because the actual distance 

 travelled is far less than on the screen 

 and the time much greater. The Wis- 

 tar Institute of Anatomy in Philadel- 

 phia is distributor of a comprehensive 

 series of motion picture films on either 

 a purchase or rental basis. 



Motor End Plates. The particular morpho- 

 logical type of nerve ending in muscle 

 does not concern us here ; but reference 

 can be made if desired to the classifica- 

 tion by Hines, M., Am. J. Anat., 1931, 

 47, 1-55. The methods advocated for 

 histological demonstration are legion. 

 Reference is made to 2 gold techniques 

 (Craven's and Carey's) and to 1 silver 

 method (Chor's). The former can be 

 ultimately traced back to Ranvier and 

 the latter to Cajal. See also techniques 

 described under Nerve Endings. 



Mounting Media. The refractive index of 

 the medium is important and a table 

 giving the indices for many substances 

 used is supplied by Lee (p. 218). As 

 pointed out, the greatest transparency is 

 secured when the refractive indices of 

 media and tissues are equal and media of 

 lower index than the tissues give some- 

 what greater visibility of tissue com- 

 ponents, while those of higher index 

 provide less visibility. There are nmny 

 media to choose from, the refractive 

 indices of which are more or less satis- 

 factory. The selection will depend 



more upon whether the medium can be 

 employed for the particular tissue and 

 its relative permanence. 



For frozen sections and tissues to be 

 mounted from water and aqueous solu- 

 tions various glycerin mixtures are 

 popular : Lactophenol, Glychrogel, 

 Brandt's and Kaiser's glycerin jellies. 

 Having taken the easiest one to prepare, 

 for their merits are about equal, the 

 tissue is mounted and covered and it is 

 necessary to seal the edges. In the case 

 of temporary mounts a little paraffin 

 applied with a heated scalpel, or wire, 

 will suffice. Lee (p. 230) advocates 

 Peter Gray's sealing medium made up 

 by melting together 4 parts anhydrous 

 lanolin, 1 part Canada balsam (dry) and 

 8 parts resin which becomes solid on 

 cooling. Apply to edges in the same 

 manner as the paraffin. Eronig's ce- 

 ment is employed in Bensley's labora- 

 tory. Duco cement is very worthwhile 

 because it is insoluble in xylol, alcohol 

 and other chemicals used to clean micro- 

 scopic preparations. Mallory (p. 99) 

 dilutes it with an equal volume of ace- 

 tone. See Karo. 



For sections and tissues which are first 

 dehydrated and cleared the investiga- 

 tor must choose the mounting medium 

 best adapted to his purpose from a con- 

 siderable number proposed of which the 

 following are given elsewhere in this 

 book : Balsam, Cedar Oil, Clarite, 

 Colophonium, Damar, Diaphane, Eupe- 

 ral, Nevillite, Sandarac, Terpineol 

 Balsam. 



The chief desiderata are a medium 

 which will harden fairly quickly, which 

 will not become acid and bring about the 

 fading of anilin dyes and which will not 

 crack or develop granules. Clarite is 

 competing for first place with balsam* 

 because, to make the balsam neutral ana 

 keep it so, is a troublesome job. Direc- 

 tions for its preparation are given by the 

 Bensleys (p. 39). But the balsam ordi- 

 narily purchased is satisfactory for 

 hematoxylin and eosin and iron hema- 

 toxylin preparations except when the 

 latter are counterstained with an anilin 

 dye. The writer used to employ cedar 

 oil (for immersion objectives), in mount- 

 ing sections stained by Giemsa's 

 method, which is superior to balsam, 

 but it drys slowly and is not better than 

 clarite. Damar has been recommended 

 for stains likely to fade and colophonium 

 for thick sections of the nervous system 

 for which covers are not used; both 

 however appear to be less valuable than 

 clarite. 



Museum specimens require an aque- 

 ous mounting medium which preserves 



