302 PROCEEDINGS OF THE NATIONAL MUSEUM. 



The addition of common salt to formalin solutions acts veiy much 

 like larger proportions of formalin alone. The initial rise is shortened 

 and reduced; in stronger concentrations it is replaced in twent3'-four 

 hours by loss; but the subsequent loss in weight proceeds much like 

 that in simple formalin solutions." 



Additions of alum to formalin solutions cause, though the specific 

 gravities of the resulting liquids are less, a greater loss in brain weight 

 than the liquids with similar additions of common salt. The weaker 

 solutions caused a smaller initial (one week) but a greater subsequent 

 loss than the concentrated one.^ 



The mixtures of alum, common salt, and formalin are characterized 

 by the great loss which they produce in the weight of the specimens 

 after the first week. There is no advantage whatever in these solu- 

 tions. 



The three mixtures of alcohol with formalin all show an initial loss 

 in the weight of the specimens, but subsequenth" there is a relatively 

 great stability. Several of the groups (particularlj^ with Stroud's 

 liquid) show actually a little gain following the initial loss. As the 

 proportion of the formalin in any of the solutions is quite insignificant 

 (1 per cent), these effects must be referred nearly wholl}^ to the alco- 

 hol and water in the solutions, with the action of which, so far as our 

 knowledge goes, thev agree. '^ 



Individual variation was present with all the liquids used, most in 

 the 1.5 per cent formalin and the 1,080 specific gravity common salt 

 solution with 5 per cent formalin, least in the 'ob parts of alcohol with 

 35 parts of 3 per cent formalin (two specimens only) and in the sodium 

 acetate-sodium-chloride-alcohol-formalin mixture. In a large major- 

 it}' of the preservatives the variation was greater at the end of the 

 first month than at the end of the first week; after that it still increased 

 with some solutions, while with others it grew less. 



The most potent discernil)le cause of this individual variation was, 

 as in the cases dealt with in the first part of this paper, the difference 

 in size of the specimens. Another ascertainable cause, but operative 

 to a less extent, was the relative quantity of the preservatives. Even 

 with the sheep brains alone the large ones suffered in the same rela- 

 tive quantity of preservative less change, particularl}- less ultimate 

 loss, than the small ones; and a double quantity of the liquid, even 

 though most brains chosen for the experiment were large ones, resulted, 

 in the majority of instances, in a loss of weight markedly greater than 

 the average in the smaller proportion of the solution. The variations 

 ■which remain unaccounted for are of obscure and probably complex 



« A greater whiteness of the specimens was again noticeable. 



6 All the specimens showed very good hardening. The diniinution in size in those 

 in the concentrated ."Solution was very noticeable. 

 "See Donaldson, Jour. Morphol., 1894, p. 149. 



