GELATIN METHOD 97 



GELATIN MASSES 



179. Gelatin Imbedding is a method that has the advantage of 

 being a])plieahlc to tissues that l^ive not been in the least degree 

 dehydrated. 



The modus operandi is, on the whole, the same as for other 

 fusion masses, with the difference that the objects are prepared 

 by saturation with xvater instead of alcohol or a clearing agent. 

 After the cooling of the mass it may sometimes be cut at once, 

 but it is generally necessary to harden it. This may be done by 

 treatment for a few minutes with absolute alcohol (Kaiser), 

 or for a few days with 90 per cent, alcohol (Klebs) or chromic 

 acid (Klebs), or formaldehyde (Nicolas), or it may be frozen 



(SOLLAS). 



The mass can be removed from the sections by means of warm 

 water. 



Gelatin imbedding has been used by Nicolas {Bibliogr. Anat., 

 3, 1896, p. 274), Olt {loc. cit.), and Gaskell (J. Path. Bact., 1912, 

 p. 58) to improve the freezing technique, but these workers had 

 trouble in the subsequent handling of the tissues. Zwemer 

 {Anat. Rec, 57, 1933, p. 41) has improved on the earlier methods 

 and his technique is given below : — After fixing in formalin, or 

 some other way, the tissue is washed and then placed in a 5 per 

 cent, solution of gelatin in an incubator at about 37° C. for twenty- 

 four hours. It is then placed in a 10 per cent, solution of gelatin 

 at the same temperature for about twelve to sixteen hours. The 

 tissue is now imbedded in a 10 per cent, solution of gelatin, in a 

 dish of convenient size and placed in a refrigerator for a few hours 

 until the gelatin hardens. Blocks of gelatin containing the 

 tissue are cut out and dropped into a 10 per cent, solution of 

 formol and left for several hours to make the gelatin insoluble in 

 water. They can be left in this solution indefinitely. Before 

 sectioning the blocks are rinsed in water and trimmed down 

 close to the tissue. They are then frozen in dry CO.^ gas until the 

 blocks are a uniform white, and then they are allowed to thaw 

 until the knife will cut real slices. Section rapidly while con- 

 ditions are favourable. Sections as thin as 5 micra have been 

 obtained by this procedure. 



The sections may be transferred, with a camel-hair brush, to a 

 dish of distilled water, if they are to be mounted immediately, 

 or they can be kept indefinitely in a 10 per cent, solution of formol. 

 Sections are transferred to a clean glass slide and after the water 

 is removed a drop or two of 1 per cent, gelatin is run under the 

 section. Now the slide is dried for five minutes at about 35° to 

 37° C. and then placed in a 10 per cent, solution of formol to fix 

 the gelatin. After rinsing, the section is ready for staining as 

 desired. Afterwards, a mounting medium called " Glychrogel " 



VADE-MECUM. 4 



