410 HALBERT L. DUNN 
Weight. The ponderal determinations were made on a scale 
accurate to 0.01 gram. Before weighing in every instance the 
brain part was stripped of its meningeal coverings and was placed 
on a pad of dry gauze for 30 seconds to remove approximately the 
same amount of surplus fluid in each case. Weights were always 
taken upon preserved material. 
Volumes. The volumetric determinations were made with a 
special apparatus constructed according to a plan suggested by 
Prof. L. W. Jones, formerly of the Department of Chemistry of 
the University of Minnesota. A sketch of this device is shown in 
figure 1. It consists of an iron chemical stand (A) to which a 
clamp (B) is attached. This clamp holds a hard-rubber stopper 
(C), to which is attached a slender wire (D) about 15 cm. inlength. 
A small disk of mica about 1 cm. in diameter slides freely on this 
wire. The wire is suspended in a jar or wide-mouthed bottle 
(F) which has a spigot at its base and which is partially filled with 
water. In using the apparatus the water in the bottle is drawn 
off until the mica disk which floats on its surface touches the hair 
line on the wire. The mass to be measured is then placed in the 
bottle and the level of the fluid rises, carrying the disk with it. 
The water is then drawn off into a beaker of known weight until 
the mica disk has sunk again to the level of the hair line on the 
wire. The beaker with the contained water is then weighed and 
the known weight of the beaker is subtracted from the total, thus 
giving the weight of the water displaced by the brain part. 
After the proper temperature correction, this value can be con- 
verted into a measure of volume. With practice and proper pre- 
cautions, it is possible to determine small volumes quite accurately 
with this apparatus. When working with small bodies, it is de- 
sirable to use a bottle with a capacity of not over 30 to 40 ce. 
A difference of approximately 0.1 cc. in volume can be determined 
without trouble if a small container is used. 
The lineal, volumetric, and ponderal determinations made were 
as follows: 
1. CH: Crown-heel length, or total body length; from the 
vertex to the tip of the heel. 
2. CR: Crown-rump length, or the sitting height; from the 
vertex to the tip of the coccyx. 
