KILLING. 



CHAPTER II. 



KILLING. 



6. In the majority of cases, the first step in the preparation 

 of an organ or organism consists in exposing it as rapidly and 

 as completely as possible to the action of one of the Fixing 

 Agents that are discussed in the next chapter. The organ or 

 organism is taken in the normal living state ; the fixing agent 

 serves to bring about at the same time, and with sufficient 

 rapidity, both the death of the organism and that of its histo- 

 logical elements. 



But this method is by no means applicable to all cases. 

 There are many animals, especially such as are of a soft con- 

 sistence, and deprived of any rigid skeleton, but possessing a 

 considerable faculty of contractility such as many Coelen- 

 terata, Bryozoa, and Serpulida, for instance which if thus 

 treated contract violently, draw in their tentacles or branchiae, 

 and die in a state of contraction that renders the preserved 

 object a mere caricature of the living animal. In these cases, 

 special methods of killing must be resorted to. 



Sudden Killing. 



7. Speaking generally, there are two ways of dealing with 

 these difficult cases. You may kill the animal so suddenly 

 that it has not time to contract ; or you may paralyse it by 

 narcotics before killing it. 



The application of heat is a good means of killing suddenly. 

 It has the great advantage of allowing of good stnmiu^- subse- 

 quently, and of hindering less than any other method the 

 application of chemical tests to the tissues. By it, the tissues 

 are fixed at the same time that somatic death is brought about. 

 And what is more, the fixation thus brought about is extremely 

 faithful, provided the operation be properly performed. 



