(c) Saturated water solution of red ferricyanide of potassium.
(d) Saturated water solution of oxalic acid.
Make a solution (1) by adding 30 cc. of a to 12 cc. of b, and a solution (2) by adding 24 cc. of c to 60 cc. of a; both mixtures to be made at a temperature of 30°C. At same temperature add 24 cc. of d to solution 2, and then solution 1, stirring constantly so that Berlin blue is precipitated. Heat on a water-bath to 90°C.; filter through flannel.
3. Fischer’s Milk-Method. The vessels are flushed with 8 per cent sodium nitrate or sulphate solution, and then injected with milk. When sufficiently injected the tissue is hardened for 24 hours in a solution of water, 1,000 cc., formalin (40 per cent formaldehyde) 75 cc., and glacial acetic acid 15 cc. Freeze, cut and stain with Sudan III or Scharlach R.; the course of the vessels is outlined by the fat-globules.
4. Silbermann’s method of injecting indigo-carmine, eosin or phlosin-red into the circulating blood has been used for the demonstration of capillary thrombi, the latter remaining free from the pigment.
12. Warm Stage. For the study of vital phenomena in the living cell Ross’s electrical warmer is recommended. It can be slipped on and off the slide without changing the focus, and is managed without any difficulty. It keeps the centre of the slide at a temperature of 37°C. Reagents can be applied as desired. Deetjen’s agar may be used as a medium for the preservation of living cells. (See Methods of Blood-Examination.) Various forms of warm and moist chambers used in experimental embryological work can also be utilized in experimental pathology.
13. Tissue-cultivation. The embryologic methods of growing tissues in lymph and blood-plasma as developed by Harrison, Burrows and Carrel have been applied in pathologic work to the experimental study of repair and regeneration, grafting, transplantation and tumor-transplantation. (For methods see Harrison, Journal of Exper. Zoology, 1910; Burrows, Jour. of Amer. Med. Assoc., 1910; Carrel, Jour. of Amer. Med. Assoc., 1910.)
II. REAGENTS USED IN THE EXAMINATION OF FRESH TISSUES.
In the examination of fresh tissue it is often desirable to use certain reagents for the purpose of making chemical tests or to bring out some structures more prominently than others. To introduce these reagents beneath the cover-glass in such a way as to get the desired effect without disturbing given fields requires some practice with a very simple technical method. The preparation is first examined in salt-solution, and the cover-glass adjusted so that it has a slight rim of fluid about its edge, but not enough to make it float. The reagent to be applied is dropped with a glass-dropper at one side of the cover-glass, while at the other the salt-solution is removed slowly by a piece of absorbent paper. The changes produced in the tissue-elements during the progress of the reagent can be observed under low or high powers. Care must be taken to change the fluids so slowly that isolated cells will not be washed away.
1. Physiologic or Indifferent Fluids. Serous exudates, blood-serum, hydrocele fluid, etc.; artificial serum made by a mixture of 9 parts physiologic salt-solution with 1 part white of egg; or physiologic salt-solution (0.9 per cent for warm-blooded animals, 0.6 per cent for cold-blooded).