NO. 1451. BRAINS AND BRAIN PRESERVATIVES— HRDLICKA. 247 



in a city to obtain in fresh condition large numbers of heads of 

 slaughtered animals. Utilizing both resources, a double plan was fol- 

 lowed. A number of ditferent formalin solutions was made up, some 

 in concentrations used l)y other workers and a few empirically as to 

 strength, and each solution was used on a series of brains as the}^ were 

 received, including specimens of every nature. The second proced- 

 ure was to obtain a large number of brains, as far as possible in the 

 same condition, from some one fair-sized animal, and to subject uni- 

 form series of such brains to the action of different solutions. The 

 results of this latter inquiry appear in the second part of this paper. 



There are numerous factors which, as Donaldson has already shown, 

 aft'ect the changes in the brain in the same solution. One of these is 

 the degree of freshness of the brain; another is the temperature of 

 the air (large differences); and still another is the presence or absence 

 of the soft membranes. Only the last of these conditions was capable 

 of being fully regulated in the National Museum collection. The 

 subjects from which brains are here obtained come from different 

 sources, and it is impossible to get all the brains equally fresh; and as 

 to cold and heat, the collecting continues throughout the year, and the 

 laboratories are not so fitted as to keep up an even temperature. Yet 

 no specimens were included in the tests that were sufficiently advanced 

 in decomposition to make their hardening and preservation doubtful; 

 and the changes of temperature in the laboratory where the brain col- 

 lection is stored would not exceed 40° F. as the maximum in the 

 course of the year. The brain w^as always laid into the preservative 

 with the soft membranes intact or but slightly injured. 



The regular procedure in cases of the first category was as follows: 

 The brain, being extracted without the dura mater, was immediatel}^ 

 Aveighed; the solution in which it was to be laid was prepared before- 

 hand; a layer of absorbent cotton was placed on the bottom of the 

 glass jar to be used, and a quantity of the preservative poured in; the 

 brain was then placed into the solution, with its base dow^nward on the 

 cotton, so as to rest easily (the cerebellum and cerebrum in the larger 

 brains being separated by a thin layer of cotton), and a sufficient quan- 

 tity of the preservative was added to rise 1 to li inches above the speci- 

 men. The jar was then closed, labeled, and placed on a shelf, where 

 it remained for one week. No injection through the arteries or into 

 the ventricles was practiced, because it would have been impossible 

 with all the specimens, and it was not found essential. On the eighth 

 day the brain was taken out, drained in a fixed manner, and then 

 weighed; the old cotton and solution were replaced with new, in same 

 quantity, the brain was put back into the jar and placed again on the 

 shelf. One month after receiving the specimen the same procedure 

 was repeated. Other weighings were taken in some cases, during as 



