| For Injecting. | For Immersing. | |
| Arsenious acid | 16 grams | 12 grams |
| Sodium chloride | 80 grams | 60 grams |
| Potassium sulphate | 200 grams | 150 grams |
| Potassium nitrate ... | 25 grams | 18 grams |
| Potassium carbonate... | 20 grams | 15 grams |
| Water | 10 litres | 10 litres |
| Glycerine | 4 litres | 4 litres |
| Wood naphtha | 0.75 litres | 0.75 litres |
My friend, Dr. Priestley Smith, surgeon to the Birmingham Eye Hospital, has kindly given me his formula for a process which most admirably preserves delicate parts of animals. Having been enabled to give him some eyes of rare animals and fishes (whales and sharks), he showed me the process which is now fully explained in the following extract from the British Medical Journal of Jan. 10th, 1880:
PRESERVATION OF OPHTHALMIC SPECIMENS.
Several friends and correspondents have asked me to refer them to a description of the method which I employ for the preservation of ophthalmic specimens, examples of which were exhibited in the annual museum of the Association in Cork last summer. I published an account of it in the Birmingham Medical Review for July, 1878; but, as several improvements have been effected since that time, I shall be greatly obliged by being allowed space in this journal for a brief description of my present method.
No. 14. — Priestley Smith's Formula.
The following are the solutions, etc., employed:
1. Mueller's Fluid — viz.,
Bichromate of potash 1 part,
Sulphate of soda 1 part,
Water 100 parts;
2. Hydrate of chloral and water, 1 in 20;
3. Glycerine and water, 1 in 4,
4. Glycerine and water, 1 in 2 — i.e., equal parts;
5. Glycerine-jelly — viz.,
Best French gelatine 1 part,
Glycerine 6 parts,
Water 6 parts,
Soak the gelatine in the water until swollen,
then heat and add the glycerine,
add a few drops of a saturated solution of carbolic acid, and
filter hot through white blotting-paper;
6. A thick white varnish made by mixing oxide of zinc with copal varnish in a mortar.
The eyeball is placed, immediately after excision, unopened, in Mueller's Fluid for about three weeks, light being carefully excluded. It is then frozen solid by immersion for a few minutes in a mixture of finely powdered ice and salt, and immediately divided into lateral halves by means of a sharp-edged table-knife. The portion to be mounted is then placed in chloral solution for some weeks, in order to remove the yellow colour; light being still excluded, and the fluid being changed until it is no longer discoloured by the bichromate. The specimen next lies for twenty-four hours or longer in the weaker glycerine solution, and is then transferred for a similar period to the stronger glycerine solution, after which it may be mounted in the jelly without danger of shrinking. A specimen-jar being two-thirds filled with melted jelly, the half-eye is placed in it, the concavity upwards. When every interstice is filled, it is turned over (care being taken to avoid the inclusion of an air-bubble), and held in a central position in contact with the bottom of the jar. When cold and firmly coagulated, the jelly is coated over with white varnish. A few days later, when the surface of the varnish is firm, this again is thinly coated with a film of jelly, and thereby preserved from the ultimate danger of cracking. The jar is fixed with glue into a suitable wooden stand. The gelatine which yields the strongest and most colourless jelly is that manufactured by Coignet and Co., of Paris, obtainable in packets, and known as the "gold-label" variety. The specimen-jars, admirable both as to material and workmanship, have been made expressly for me by Messrs. F. and C. Osler, of Broad Street, Birmingham, from whom they may be obtained in any number. — PRIESTLEY SMITH, Birmingham.
Glycerine retards fermentation and decomposition to a remarkable degree. It combines readily with alcohol or water.