CONCENTRATION 



72 



CONTRACTION BANDS 



elements behind. Then a little saline 

 solution is added and the material is 

 ground up in sand and made up to a 

 volume of about 50 cc. The sand is 

 allowed to sediment out at the bottom 

 of a centrifuge tube. The supernatant 

 fluid is then centrifuged at low speed 

 (300 r.p.m.). This throws all the rest 

 of the debris to the bottom while the 

 bacilli remain in suspension. The 

 supernatant fluid, containing the bacilli, 

 is again decanted and centrifuged at high 

 speed (3500 r.p.m.) in an angle 

 centrifuge for 1 hr. The supernatant 

 fluid is discarded and the pasty material 

 at the bottom of the tube, made up of 

 bacilli, is diluted and washed by re- 

 peated centrifugation in some experi- 

 ments with saline solution and in others 

 with distilled water. 



Beginning with a large nodule or with 

 several small ones it is a simple matter 

 to collect in 4 or 5 hrs. billions of bacilli. 

 The pasty bacterial mass can be desic- 

 cated and weighed in grams. For our 

 experiments we used only the wet 

 bacilli. When viewed en masse they 

 appear dense white with a faint shade 

 of gray. They are not yellow or even 

 yellowish. Examination of a thick 

 smear, made after washing in saline, 

 shows myriads of bacilli without any 

 trace of cellular material. The bacilli 

 retain to a remarkable degree their 

 characteristic morphology, as seen in 

 sections and in smears of fresh tissue, 

 and their acid-fast properties are not 

 interfered with. After washing in 

 distilled water until the supernatant 

 fluid gave no precipitate when added 

 to an aqueous solution of silver nitrate, 

 the bacilli do not fuse together but still 

 remain discrete bodies though their 

 shape is different. (Cowdry, E. V., 

 Ravold, A. and Packer, D. M. Proc. 

 Soc. Exp. Biol. & Med., 1939, 41, 341- 

 345). See Floatation Techniques for in- 

 testinal parasites. 



Congo Blue 3B, see Trypan Blue. 



Congo Corinth G or GW, see Erie Garnet B. 



Congo Red (CI, 370). Synonyms: Congo, 

 cotton red, A, B or C, direct red C, R or 

 Y. An acid dis-azo dye which is an 

 excellent indicator and a useful stain. 

 Matsuura, S., Fol. Anat. Jap., 1925, 3, 

 107-110 has obtained very fine coloration 

 of the skin which he has illustrated in 

 colors. Congo red is the basis of Kra- 

 jian's stain for elastic fibers. See also 

 Blackman, V. H., New Phytol., 1905, 

 4, 173-174 (uredineae); Merton, H., 

 Arch. Protistenk., 1932, 76, 171-187; 

 Cumley, R. W., Stain Techn., 1935, 

 10, 53-56 (negative stain for bac- 

 teria), etc. 



Connective System. Provides both for the 

 binding together of parts and for their 



separation one from another by capsules, 

 membranes and other structures (see 

 Cowdry, p. 429-466). It ranges all the 

 way from Loose Connective Tissue 

 and Fatty Tissue through Fibrous 

 Connective Tissue and Tendons to 

 Cartilage and Bone. Neuroglia is a 

 special form of it. In general there are 

 three components, Fibroblasts, Fibers 

 and Tissue Fluid (ground substance). 

 Cells of hematogenous and lymphatic 

 origin may be present since blood vessels 

 and lymphatics run in connective tissue 

 pathways. See techniques under these 

 headings, also Masson's Trichrome 

 Stain, Mallory's Connective Tissue 

 Stain, Phosphomolybdic Acid Hema- 

 toxylin, Van Gieson, Buzaglo, etc. 



Connective Tissue Cells, preservation of 

 trypan blue and neutral red in those of 

 loose connective tissue. Inject sub- 

 cutaneously 5 cc. fresh sterile 1% aq. 

 vital trj^pan blue (Coleman and Bell 

 Co.) into a mature wliite rat weighing 

 about 90 gms. and wait 48 hrs. Make up 

 0.02% certified neutral red (National 

 Aniline in 0.9% NaCl). After slight 

 etherization exsanguinate the animal. 

 Inject neutral red into subcutaneous 

 tissue of groin in several places near 

 original puncture. After 3-5 min. re- 

 move small blobs of edematous tissue. 

 Tease these out on clean slides with aid 

 of needles and filter paper. When 

 corners are dry spread is ready for 

 direct ol^servation under cover glass or 

 for fixation. Make up 10% formalin. 

 Test it by addition of a drop or two of 

 neutral red. If this turns orange add 

 a little N/10 HCl until it becomes red. 

 Fix in this formalin over night or for 

 several da j^s . Rinse in aq. dest. Coun- 

 terstain in 1% fast green F.C.F. (War- 

 ner-Jenkinson Co.) in 2% aq. acetic 

 acid for ^1 min., pass through suc- 

 cessive changes dioxan, 3-5 min. each. 

 Agitate slightly. Mount in dioxan 

 employing medium hardened diaphane 

 (Will Corp.), redissolve in dioxan or 

 pass through xylol and mount in balsam. 

 Avoid alcohols. Note blue granules in 

 macrophages and fine red granules in 

 mast cells (Snook, T., Stain Techn., 

 1939, 14, 139-142). See Connective 

 System. 



Contraction Bands, or waves, demonstration 

 of in smooth muscle. Remove intestine 

 of freshly killed cat, expose to air of room 

 or rub with blunt end of scalpel. When 

 preparations are made numerous con- 

 traction bands will be seen. Contrast 

 with this intestine of cat killed with 

 chloroform and not excised until rigor 

 mortis begins in which muscle fibers 

 are fully extended (Dahlgren, McClung, 

 p. 430). 



