60 FIXING AND HARDENING AGENTS 



the desired method (Bouin formol), transfer to Carnoy, then absolute 

 alcohol. 



G. S. Sansom's Carnoy Modification. 



Absolute alcohol ... 65 c.c. 



Glac. acetic acid .... 5 ,, 



Chloroform . . . . . 30 „ 



Corr. subl. to saturation. Leave ten minutes to half an hour ; wash 

 in iodine absolute, then absolute. (Personal communication.) 



Eminently suitable for study of vertebrate material. We have seen 

 some really brilliant results obtained by the use of this fluid (§ 807). 



92. Trichlor-acetic Acid (Holmgren, Anat. Hefte, xviii, 1901, 

 H. 2). This substance is one of the best decalcifying fluids known 

 (§ 601). But swelling of collagen fibres takes place if the fixed 

 material is put in water afterwards. Trichlor-acetic has been used 

 in a number of recent histological fixatives. Use a 4 or 5 per cent, 

 solution in water. Fix (nerve-cells) for eight to twenty-four hours, 

 wash out with alcohol. See also Heidenhain, Zeit. wiss. Mikr., 

 xxii, 1905, J). 321, and xxv, 1909, p. 405, who makes a mixture of 

 6 per cent, sublimate solution with 2 per cent, of trichlor-acetic 

 and 1 per cent, of acetic acid, which he calls " Subtriessig." 



93. " Susa " Fixatives. The so-called " Susa mixture" of 

 Heidenhain is as follows : sublimate 4-5 grm., common salt 

 0-5 grm., distilled water 80 c.c, trichlor-acetic acid 2 grm., acetic 

 acid 4 c.c, formol 20 c.c Fix one to twenty-four hours, transfer 

 to 90 per cent, alcohol. Ludford informs us that the best way for 

 making it is as follows : stock solution : sublimate 4-5 grm., 

 salt 0-5 grm., water 80 c.c. To make up 10 c.c of fixative take 

 8 c.c of stock and add to it glacial acetic 0-4 c.c, formol 2 c.c, 

 trichlor-acetic 0-2 grm. 



The amount of sublimate precipitated in the tissues is slight, 

 and it is usually unnecessary to employ any methods for 

 removing it. 



Romeis " Susa " Mixture. Saturated sublimate water 25 c.c, 

 5 per cent, trichlor-acetic 20 c.c, formol 5 c.c Fix small pieces 

 one to two hours, larger ones up to twenty-four hours. Transfer to 

 80 to 90 per cent, alcohol. Recommended for amphibian larvae 

 {Zeit.f. Ges. Exper. Mediz., Bd. 6). 



Note. Trichlor-acetic acid swells collogen if the blocks are taken 

 to water after fixation. Wash out always in 90 to 96 per cent, alcohol. 



94. Trichlor-acetic Fluid for Batrachia (Champy, Arch. d. Zool. 

 Exper. et Gen., t. lii, 1913). 



Carbolic acid cryst. in sat. aq. sol. . 15 parts. 



Formol, 40 per cent. ... 4 „ 



Trichlor-acetic acid, 20 per cent. . 1-5 „ 



Outside of tissue often bad, inner parts better. 



