26 CHAPTER III. 



/. mik. Anat., lii, 2, 1898, " Ueber die Fixirungs- (Hart- 

 ungs-) Fliissigkeiten/' and that of WASIELEWSKI, Zeit.f. wiss. 

 Mik. } xvi, 3, 1899, " Ueber Fixirungsfliissigkeiten in der 

 botanischen Mikrotechnik." The results of these authors are 

 in the main in agreement with my own, but not entirely. 

 The points of difference are probably to a great extent to be 

 explained by the fact of these observers having each of them 

 confined his attention to a single category of cells. Now it 

 is by no means true that that which fixes one sort of cells 

 well or ill will also fix the majority of others in a similar 

 way. 



29. The Practice of Fixation. Hints and Cautions. See that 

 the structures are perfectly living at the instant of fixation, 

 otherwise you will only fix pathological states or post-mortem 

 states. 



Do all you can to facilitate the rapid penetration of the 

 fixing agent. To this end let the structures be divided into 

 the smallest portions that can conveniently be employed, 

 and if entire organs or organisms are to be fixed whole, let 

 openings, as large as possible, be first made in them. 



The penetration of reagents is greatly facilitated by heat. 

 You may warm the reagent and put it with the object to be 

 fixed in the paraffin stove, or you may even employ a fixing 

 agent heated to boiling-point (as boiling sublimate solution 

 for certain corals and Hydroids, or boiling absolute alcohol 

 for certain Arthropods with very resistent integuments). 

 But this should only be done as a last resource. 



Let the quantity of fixing agent employed be at least many 

 times the volume of the objects to be fixed. If this precaution 

 be not observed the composition of the fixing liquid may be 

 seriously altered by admixture of the liquids or of the soluble 

 substances of the tissues thrown into it. For a weak and 

 slowly acting fixing agent, such as picric acid, the quantity of 

 liquid employed should be in volume about one hundred times 

 that of the object to be fixed. Reagents that act very ener- 

 getically, such as Flemming's solution, may be employed in 

 smaller proportions. 



BBATJS and DRUENER (Jena. Zeit. Naturw., Bd. xxix, 1895, p. 435) fix 

 fishes ~by injection through the bulbus aortx. The vessels are first washed 

 out with normal salt solution, the fixing liquid is then thrown in, then as 



