ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 247 



MICROSCOPY. 



B. Technique. 



Cellular Changes in Cartilage Grafts. — J. A. Murray {Sci. Rep. 

 Imp. Cancer Remi.rch Fund., 1910, 6, 71). Slow degenerative changes 

 take place in the cells of cartilage grafts. Accompanying the de- 

 position of fat-globules, which is probably only an exaggeration of what 

 occurs in undisturbed cartilage, there are nuclear changes regarded 

 by Murray as amitotic. In a human autologous graft irregular achro- 

 matic spindles and attraction spheres were found and figured. The 

 paper describes the methods found useful by the author for the study 

 of cartilage grafts. As they are of more general application they are 

 given here in greater detail : — 



Gelatin Slides for Frozen or Gum Sections. — Clean slides are coated 

 with a film of 1 p.c. gelatin in distilled water. The film must be as 

 thin as is compatible with the formation of a continuous layer, spread 

 with a glass rod or slide (like a blood film). The slides are put aside 

 to dry and kept till required. To fix sections on slides, immerse the 

 slide in water containing the sections in a flat dish. Arrange in 

 position with a glass rod, withdraw the slide with the sections on it, 

 and drain off the superfluous water. Lower a wet cigarette-paper over 

 the sections, and dry by pressing on firmly a thick layer of absorbent 

 paper (blotting or filter). Strip off the cigarette-paper and place the 

 slide in a tube, with a wad of cotton soaked in commercial formalin at 

 the bottom. In two to four minutes the gelatin film will be sufficiently 

 hardened to keep the sections in position. Complete the fixation by 

 immersing the slide in a bottle of 10 p.c. formol in 0*8 p.c. salt solution. 

 Staining can now be carried out without fear of the sections coming 

 adrift, unless hot mineral acid solutions are used for more than ten 

 minutes. 



SalkincVs Lead-gum Imbeddinfj Method {G.R. Soc. Biol, 1916, 79, 

 811). — An aqueous solution of gum arable, treated with lead acetate, is 

 transformed into a gel on exposure to vapour of ammonia. On addition 

 of acetic acid it returns to the sol condition. This is the basis of the 

 imbedding method, which is as follows : — 1. Dissolve cherry-gum 

 (white), 1 part (by wt.), in aq. dest., 2 parts (by wt.). 2. Filter (this 

 is usually very slow, and I usually use more water. The yellow and 

 brown samples of gum practically will not filter). 3. Add to the 

 clear solution one-third of its volume of liq. plumbi subacetatis fort., 

 containing 5 p.c. acetic acid. 4. The tissues* to be cut are soaked in the 

 clear solution so prepared, usually 12 hours for each millimetre in 

 thickness. They may be kept in it indefinitely. 5. To prepare for 

 cutting, allow the water to evaporate at room temperature till the liquid 

 is of the consistency of thick collodion solution. 6. Arrange the piece 

 in a drop of thickened gum on a wooden block and expose to ammonia 



