N0.1451. BRAINS AND BRAIX PRESERVATIVES— IIRDLICKA. 249 



tion of formalin increased, which showed that the effe(;t of formalin on 

 the brain was to hinder its enlaro-enient (apparently due to water 

 alone) and probably, in addition, to promote the loss of some of the 

 constituents of the organ. After the culmination of the process of 

 gain, which, as shown bv further experiments, was always completed 

 before nine days, a gradual progressive loss followed, which in per- 

 centage was alike with the different solutions. The ultimate weight 

 of the l)rain depends, in consequence of this similarity of loss, very 

 largel}^ on the height of the initial rise in weight. If this had been 

 large, as with the 3 per cent solution, the ultimate weight (within two 

 3"ears) would still be above the original; but if the gain was smaller, 

 as with the 15 per cent formalin solution, the ultimate weight of the 

 specimen would be found more or less below its weight imn)ediately 

 after extraction from the skull. 



Whenever a marked increase in the weight of the brain took place, 

 there was also a noticeable increase in its volume. 



The eifect of adding alum or salt to formalin solutions was to 

 decrease or, with larger quantities, almost entirely to do away with the 

 initial gain, and to augment the subsequent absolute loss of brain weight. 

 The percentage of the loss in weight, however, remained related to 

 that in the simple formalin solutions, Simultaneousl}" with the loss of 

 weight in the stronger concentrations was also visible a decrease in 

 the volume of the organ. No direct relation was found between 

 these phenomena and the specific gravit}" of the solutions. It appears 

 that alum, sodium chloride, and, according to more recent experiences, 

 other salts also, as well as, alcohol, act on the brain physicall}' much like 

 greater proportions of formaldeh3"de; hence the use of such means 

 with formalin permits the obtaining of similar physical results with 

 correspondingly smaller proportions of this chemical. 



A renewal of the preservative generally affected slightly the changes 

 in the brain, causing a temporary rise in weight. 



As to the rapidity of hardening and other visible changes in the 

 brain, the differences between the several liquids were not great. A 

 moderate toughening of the brain was in every one of the preserva- 

 tives observable on the second day, and a good hardening, with fresh 

 adult specimens, was generally reached within a week. In the salt- 

 formalin solution the brains were, at least for a time, slightly softer, 

 in the alum-formalin solution slightl}" more resistant, than those pre- 

 served in simple solutions of formalin of the same strength. A higher 

 [ percentage of formalin was favorable to a more rapid and perhaps a 

 slightl}' greater hardening. On the whole, should one be given speci- 

 mens of the same size, but each hardened in a different solution of 

 those here dealt with, after the}^ had lain a few months in the liquid, 

 it would be quite impossible b}^ the hardening alone, as perceptible 

 through the unaided touch, to distinguish an}' of the preparations. 



