194 EXAMINATION AND PRESERVATION MEDIA. 



merest incipience of putrefaction will spoil the preparation. 

 The flask should have a wide bottom, so that the serum may 

 form only a shallow layer in it; otherwise the upper layers 

 will not be sufficiently exposed to the action of the iodine. 



Another method is as follows : Serum is mixed with a 

 large proportion of tincture of iodine ; the precipitate of 

 iodine that forms is removed by filtration, and there remains 

 a strong solution of iodine in serum. This should be kept in 

 stock, and a little of it added every two or three days to the 

 serum that is intended for use. 



Ranvier explains that at the outset serum dissolves very 

 little iodine; but if an excess of iodine be kept constantly 

 present in the solution, it will be found that after two or 

 three weeks iodides are formed, and allow fresh quantities of 

 iodine to dissolve ; so that after one or two months a very 

 strongly iodised serum is obtained. It should be dark brown. 

 Such a solution is the most fitting for the purpose of iodising 

 fresh serum in the manner directed above, and for making 

 the different strengths of iodised serum that are required for 

 different purposes. In general, for maceration purposes, a 

 serum of a pale brown colour should be employed. 



347. Artificial Iodised Serum (FREY, Le Microscope, p. 131). 

 Distilled water . . . . 135 grammes. 

 White of egg .... 15 

 Sodium Chloride .... 0'20 



Mix, filter, and add 



Tincture of iodine ... 3 



There is formed a precipitate, which is removed by filtering 

 through flannel ; and a little iodine is added to the filtrate. 



348. Kronecker's Artificial Serum (from VOGT et YUNG, Traite 

 d'Anat. comp. prat., p. 473. I have been unable to discover 

 the original source). 



Common salt ..... 6 grammes. 

 Caustic soda ..... 0*06 

 Distilled water . . . .1000 



349. Aqueous Humour, Fruit Juice, Simple White of Egg. 

 Require no preparation beyond filtering. They may be 

 iodised if desired. 



350. Syrup. An excellent medium for examining many 



