STAINS, ETC. 



1374 



EMBEDDING 



paraffin. A transparent soap is prepared as follows : 

 25 gm. of shavings of sodium stearate soap, and 100 

 c. c. of 96 per cent, alcohol are heated in a retort 

 over a water-bath until the soap is dissolved, and then 

 filtered. The filtrate should be transparent. If a 

 drop poured into a watch-glass solidifies into a white 

 mass, add water in small quantities until the tested 

 drop remains pellucid. Gelatin Masses are used 

 for tissues that have not been dehydrated. The objects 

 are prepared by penetration with water, instead of 

 alcohol or a clearing agent. After the mass is cooled, 

 it may sometimes be cut at once, but it is usually neces- 

 sary to harden it, which may be done by freezing or 

 by treating for a few days with 90 per cent, alcohol or 

 with chromic acid, or for a few minutes with absolute 

 alcohol. Brunotti's Cold Gelatin. Dissolve with 

 heat 20 gm. of gelatin in 200 c.c. of distilled water, 

 filter, and add 30 c.c. of glacial acetic acid and 

 1 gm. of corrosive sublimate. Soak the object in a 

 small quantity diluted with two or three volumes of 

 water, embed in the undiluted mass, and harden 

 in alcohol. This process does not require heat. 

 Gerlach's Gelatin. Gelatin 40 gm. , saturated 

 solution of arsenious acid 200 c.c, glycerin 1 20 c. c. 

 Clarify with white of egg. Objects are prepared for 

 embedding by a bath of one-third glycerin. Klebs' 

 Gelatin {Glycerin-jelly). A concentrated solution of 

 isinglass mixed with half its volume of glycerin. 

 Celloidin is stated to be a preparation of pure py- 

 roxylin. It is non-explosive, and is soluble in ether 

 and alcohol. Collodion, prepared by dissolving gun- 

 cotton or soluble cotton in equal parts of 95 per cent, 

 alcohol and sulphuric ether, is in every way as good as 

 celloidin and considerably cheaper. Celloidin should 

 be used in thin (2 per cent.) and in thick (6 per cent.) 

 solutions. The object is thoroughly dehydrated in 

 absolute alcohol, placed in a mixture of equal parts 

 of ether and alcohol for 12 to 24 hours, or longer 

 if the object be large. It is then placed for 24 hours 

 in a thin solution of celloidin, 8 gm. in 100 c.c. 

 each of alcohol and ether, and transferred from this 

 to a thick solution of celloidin, 8 gm. in 50 c.c. each 

 of alcohol and ether. Select a cork or piece of soft, 

 dry wood, and dip it in the thick celloidin solution ; 

 when dry, place the prepared tissue upon it and drop 

 the thick celloidin solution upon this with a pipet 

 until it is embedded in a jelly-like mass. Blocks or 

 cylinders of glass or vulcanized fiber serve better than 

 cork as they sink in the liquids used. Harden in 

 90 per cent, alcohol, and preserve in 70 per cent, 

 alcohol. When making sections, keep the knife and 

 section wet with alcohol. Apathy advises previous 

 smearing of the knife with vaselin, as it cuts better 

 and is protected from the alcohol. Use bergamot-oil 

 to clear. Sections may be kept in from 60 per cent, to 

 80 per cent, alcohol. Fisk's Castor-oil and Oil of 

 Thyme Method. The mixture consists of red oil 

 of thyme 3 parts, castor-oil 1 part, and is used only 

 with collodion-embedded objects. The castor-oil 

 makes the collodion slightly flexile, so that the sections 

 do not move so readily on the slide, when the balsam 

 is applied. There is no true action as a fixative, for 

 the collodion is not dissolved in any way, only softened 

 and toughened. The edge of the knife is preserved 

 for a longer time. The castor-oil gives more " body " 

 to the mixture, making a good lubricator, and floats 

 the sections readily. Very thin sections can be ob- 

 tained by absorbing the oil and coating the object with 

 a thin layer of I per cent, collodion before cutting 

 each section. This coating is also useful if there is 

 any tendency for the section to crumble or tear. The 

 mixture is highly antiseptic, and specimens may be left 



in it indefinitely, to advantage and without shrinking. 

 If the objects have been stained in toto, the process is 

 very short. If section-staining is desired, the sections 

 after their transfer to the slide, should have as much 

 of the superfluous oil removed as possible and a few 

 drops of ether-alcohol (equal parts of each) are 

 poured over them to fasten them to the slide. The 

 sections are then put into 95 per cent, alcohol to dis- 

 solve out any oil that may be left, and passed through 

 from 70 per cent, to 35 per cent, alcohol, to water, 

 stained, carried back through the same grades and 

 mounted as usual. This is one of the best and most 

 useful of methods. Von Koch's Copal Method. 

 The object is dehydrated in alcohol, placed in a thin 

 solution of copal in chloroform, made by triturating 

 small fragments of copal in a mortar with fine sand, 

 pouring on chloroform, and filtering The solution 

 is slowly evaporated by heating. When concentrated 

 enough to draw out into threads that are brittle, the 

 object is removed and allowed to dry. Sections are 

 cut by means of a fine saw, rubbed smooth on one 

 side and with the smooth side down, are cemented on a 

 slide. When the cement has hardened, the sections are 

 rubbed until they are of the requisite thinness, washed 

 in water, and mounted in balsam. This method is 

 used for the study of hard and soft structures in their j 

 natural relations. Kultschizky's Celloidin-parafhn 

 Method. After the object is taken from the ether-and- i 

 alcohol bath it is put into celloidin-solution for 24 hours, | 

 then into origanum oil, then into a mixture of origanum- 

 oil and paraffin which has been heated to 40 C, and 1 

 finally into melted paraffin. The method, is especially 

 adapted for delicate specimens. Ryder uses chloro- 

 form instead of oil of origanum. Joliet's Gum- 

 and-glycerin Method. Pure gum arabic is dis- 

 solved in water to the consistency of a thick syrup. 

 To a little of this solution in a watch-glass add 

 10 drops of glycerin, and mix. Embed the object,; 

 previously soaked in glycerin, in the mass in the 

 watch-glass and leave to dry for several days. Cut I 

 dry, dissolve the gum from the sections in water, and 

 mount in glycerin. This mass has the advantage of j 

 being transparent. Photoxylin. A substance h 

 the appearance of cotton- wool and chemically cl 

 allied to celloidin. It dissolves in a mixture of 

 and alcohol, equal parts, and is used in the sami 

 way as celloidin. It has the advantage of for 

 a mass that remains transparent. Syrup - and 

 gum Congelation-mass. Hardened brain 1 

 previously soaked in water, is well soaked in a syru] 

 made of double refined sugar 2 ounces, water 

 fluid-ounce. Wash the superfluous syrup from 

 surface and put into ordinary mucilage an hour i 

 cutting. Embed in the freezing microtome and 

 the sections into water (Hamilton). Cole ad\ : 

 parts of syrup and 5 parts of gum for the brain 

 spinal cord, retina, and all tissues liable to 

 easily. The gum is made by dissolving 4 ouno 

 gum acacia in 6 ounces of water ; the syrup, b 

 boiling I pound of loaf-sugar in I pint of watei 

 Add 5 gr. of carbolic acid to each ounce of th 

 medium. 

 Collodionization of Sections. It sometimes ha] 

 that objects, such, for example, as ova, are too delicat 

 and too easily broken to be cut in the ordinary 

 it is necessary to cover the exposed surface I) 

 cutting each section with a thin layer of collodion < 

 celloidin. The collodion should be of such consis 

 ency, from y 2 per cent, to 1 per cent, solution, tha, 

 when applied in a thin layer to a surface of pai 

 it will dry in two or three seconds without leaving 

 shiny surface. 



