262 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxx. 



or three solutions of different concentration for brains of widely differ- 

 ent mass would seem to be needed. 



Hijjhiy diluted (less than 5 per cent) and again hio-hl}' concentrated 

 (over 15 per cent) formalin solutions, and large additions of salts, are 

 disadvantageous and ought not to be employed. 



Addition of alum to the formalin solution favors the process of hard- 

 ening, and is to be reconnnended in preserving brains of the young, 

 particularly of human fcetuses. 



Among the numerous points left to be determined are the effects of 

 additional solutions, the influence of different quantities of the pre- 

 servative, and the exact daih* changes during the first month at least 

 in the specimens. Experiments made in the laborator}^ during the 

 past summer with fifteen series of sheep brains and reported in Part 

 II, will throw some light on these matters. 



The changes in individual brains of this first series are given in the 

 following tables: 



