348 PRESERVATION OF MARINE ORGANISMS 



but it is advisable to wash one's hands directly after 

 an immersion in formalin, and never to allow the 

 30 per cent, solution to dry into the skin. There are, 

 however, people whose skin is seriously affected ; the 

 skin breaks, after the manner of chilblains, with deep, 

 open cracks, which are painful, and take some time to 

 heal ; and the fingers feel numb. None of these effects, 

 however, are permanent, or in the slightest degree 

 dangerous. 



The hardening and preserving properties of formalin 

 for animal tissues were discovered independently by 

 Blum and Hermann in 1893, and probably no one has 

 been more benefited by this important discovery than 

 the marine naturalist. Previous to 1893 alcohol was 

 practically the only fluid used for the preservation of 

 marine animals. It must not be supposed that for- 

 malin has completely supplanted alcohol, though the 

 qualities of the former have been loudly praised and 

 the existence of alcohol almost forgotten by some 

 naturalists. 



Formalin has two great advantages over alcohol : 

 (i) It does not usually produce a shrinkage of the 

 tissues ; therefore it is a splendid fluid for the preserva- 

 tion of delicate, soft-bodied animals, such as jelly- 

 fishes. (2) It is a great time-saving fluid, as specimens 

 can be placed straight into formalin without requiring 

 any further attention ; whereas with alcohol it is 

 usually necessary to pass specimens through a series 

 of different grades of strength, each grade requiring 

 a certain length of time, or to change a strong grade 

 several times so as to get rid of the watery fluids within 

 the specimens. 



To marine naturalists formalin has two special ad- 

 vantages : (i) It can be diluted with sea water, as well 

 as with fresh water. When alcohol is mixed with sea 



