Fixation 



PARAFFIN SECTIONS 



95 



Selection of a Fixative 



Fixative formulas are given in Chapter 

 18; and the selection of the fixative for 

 small invertebrates has already been dis- 

 cussed in Chapter 6. When one intends to 

 section a small invertebrate, with the pri- 

 mary function of preservinj^ its parts in as 

 natural as possible a relation to each other, 

 the same fixative should be employed as is 

 recommended for those invertebrates in- 

 tended to be made into wholemounts. The 

 purpose in each case is to preserve the ob- 

 ject in as natural a shape as possible with- 

 out special regard to the preservation of 

 the fine details of the cells themselves. 



Something of the same consideration 

 applies to blocks of tissue which are to be 

 fixed in such a manner that their general 

 structure, or histology will be displayed. 

 In this case, however, there is no problem 

 of contraction of parts, so that fixatives 

 which would be quite useless for a whole 

 animal may safely be applied to a block of 

 tissue. Reference to Chapter 18 will show 

 that there are between 600 and 800 solu- 

 tions recommended for fixation, and there 

 is no general agreement as to which is the 

 best for any particular purpose. These 

 notes are therefore written only for the 

 benefit of the beginner who, presented 

 with this bewildering display, lacks the ex- 

 , perience on which to base his choice. The 

 selections given below are modified from 

 Gray 1933 (11360, 53:15). The figures 

 ' following the name and date refer to the 

 decimal classification of Chapter 18 in 

 which the formulas for these fixatives will 

 be found. Specific suggestions for the em- 

 ployment of fixatives are to be found in 

 many of the examples of the preparation 

 of shdes which occur in this book. 



A. Recommended Fixatives for Em- 

 bryos OR Whole Organs Exceeding 

 5 Mm in Thickness. 



1. FOR USE when the PRESERVATION 

 OF SHAPE IS OF PRIMARY IMPOR- 

 TANCE. 



Bensley 1915 F 1700.0010 

 Erhtzkv 1877 F 4700.0000 

 Hoyer 1899 F 3700.0000 

 Lavdowski 1894 F 6000.0010 

 Maximov 1909 F 1700.1000 



Miiller 1859 F 7000.1000 

 Orth 1S9() F 7000.1000 

 R^gaud 1910 F 7000.1000 



2. WHEN IT IS DESIRED, AS FAR AS POS- 

 SIBLE, TO PRESERVE BOTH SHAPE 

 AND PROTOPLASMIC DETAIL. 



a. When shape is of greater impor- 



t(l7lC€ 



IlcUy 1903 F 3700.1000 

 Petrunkewitsch 1933 

 F 4900.0010 



Rawitz 1895 F 5600.0040 

 Smith 1902 F 7000.1010 

 Zenker 1894 F 3700.0010 

 b. When protoplasmic detail is of 

 greater importance 

 Fol 1896 F 1560.0000 

 Gilson 1898 F 3000.00 14 

 Kohn 1907 F 3700.0010 

 Maver 1880 F 5000.0050 

 Rabl 1894 F 2300.0000 

 Tellysniczky 1898 F 3500.0010 



B. Recommended Fixatives for Small 

 Portions of Organs or Whole Or- 

 gans OR Embryos Not Exceeding 5 

 Mm. in Thickness. 

 1. when a general-purpose fix.\- 

 tive is required 

 Carleton and Leach 1938 

 F 3000.1000 



Gatenby 1937 F 6700.0040 

 Gerhardt 1901 F 3600.1010 

 Schaudinn 1900 F 3000.0000 



2. WHEN PROTOPLASMIC DETAIL IS OF 

 GREATER IMPORT.\NCE 



a. When nuclear fixation is espe- 

 cially required 



Allen 1929 F 5600.1010 



van Beneden (1905) F 3000.0010 



Carnoy 1887 F 0000.0010 



Carnoy and Lebrun 1887 



F 3000.0010 



Sanson (1928) F 0000.0010 



b. When cytoplasmic detail is espe- 

 cially required 



Champv 1911 F 1670.0000 

 Flemming 1884 F 1600.0010 

 Kultschitzkv 1887 F 4700.0010 

 Mann 1894 F 1300.0000 

 Smith 1935 F 1670.0010 



There are only two general precautions 

 to be observed in the practical application 



