ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 869 



3. Alcohol. — In the preparation of animals or parts of animals 

 for museums or histological study, it is well known that the chief 

 difficulties are met in the process of killing. Alcohol, as com- 

 monly used for this purpose by collectors, has little more than its 

 convenience to recommend it. Dr. Mayer calls attention to the 

 following disadvantages attending its use in the case of marine 

 animals : — 



(1) In thick-walled animals, particularly those provided with 

 chitinous envelopes, alcohol causes a more or less strong maceration 

 of the internal parts, which often ends in putrefaction. 



(2) In the case of smaller Crustacea, e. g. Amphipods and Isopods, 

 it gives rise to precipitates in the body-fluids, and thus solders the 

 organs together in such a manner as often to defy separation even by 

 experienced hands. 



(3) It fixes most of the salts of the water adhering to the surface 

 of marine animals, and thus a crust is formed which prevents the 

 penetration of the fluid to the interior.* 



(4) This crust also prevents the action of staining fluids, except 

 aqueous solutions, by which it would be again dissolved. 



Notwithstanding these drawbacks, alcohol is still regarded at the 

 Naples Aquarium as an excellent fluid for killing many animals 

 designed for preservation in museums or for histological work. In 

 many cases the unsatisfactory results obtained are to be attributed 

 not to the alcohol per se, but to the method of using it. Most of the 

 foregoing objections do not, as Dr. Mayer expressly states, apply to 

 fresh-water animals ; and Dr. Eisig informs Mr. Whitman that he 

 has no better method of killing marine annelids than with alcohol. 

 Judging from the preparations which were shown him, and which 

 were all beautifully stained with borax carmine, Dr. Eisig's mode of 

 treatment must be pronounced very successful. The process is 

 extremely simple ; a few drops of alcohol are put into a vessel which 

 contains the annelid in its native element, the sea-water; this is 

 repeated at short intervals until death ensues. After the animal 

 has been thus slowly killed, it may be passed through the different 

 grades of alcohol in the ordinary way, or through other preservative 

 fluids. Objects killed in this manner show no trace of the external 

 crust of precipitates which arises where stronger grades of alcohol 

 are first used. The action of the alcohol is thus moderated, and the 

 animal, dying slowly, remains extended and in such a supple con- 

 dition that it can easily be placed in any desired position. The 

 violent shock given to animals when thrown alive into alcohol 

 of 40 per cent, to 60 per cent., giving rise to wrinkles, folds and 

 distortions of every kind, is thus avoided, together with its bad 

 effects. 



4. Acid Alcohol. — In order to avoid the bad effects of alcohol, 



* Dr. Mayer first noticed this in objects stained with Kleinenberg's hema- 

 toxylin, and afterwards in the use of cochineal, where a grey-green precipitate is 

 sometimes produced which renders the preparation worthless. Such results may 

 be avoided by first soaking the objects a few hours in acid alcohol (1-10 parts 

 hydrochloric acid to 100 parts 70 per cent, alcohol). 



