VON KUPFFER, C. Studien zur vergleichenden Entwickelungengeschichte des 1893 Kopfes der Kranioten. Heft 1, Munich and Leipzig.

WILSON, J. G. The relation of the motor endings on the muscle of the frog to neighboring structures. Jour. Comp. Neur. and Psych., vol. 14, p. 1.

1904

DESCRIPTION OF FIGURES

FIG. 33. Intra-vitam methylen blue impregnation of the nerves of the pineal stalk (epiphysis) of adult Amia, as seen from the surface of a total mount showing the relation of the cells and their processes to the longitudinal fibers. Lateral limits of pineal stalk at b. X 408.

FIG. 34. From the same preparation as previous figure to show details of a cell at point a. Note the Nissl bodies and the similar structure of the different cell processes. X 1500.

FIG. 35. From the same preparation as the two previous figures, near the edge of the mount where there were not so many overlying layers of the meninges to obscure the details. X 1500.

NERVUS TERMINALIS IN AMIA

CHARLES BROOKOVER

THE JOURNAL OF COMPARATIVE NEUROLOGY AND PSYCHOLOGY-VOL. 20, No. 2.

PLATE I

ON THE PERCENTAGE OF WATER IN THE BRAIN AND IN THE SPINAL CORD OF THE ALBINO RAT

HENRY H. DONALDSON

The Wistar Institute of Anatomy and Biology

WITH FIVE FIGURES

The object of this study has been to obtain a continuous record of the change in the percentage of water in the central nervous system of the albino rat during its life cycle, and to correlate this with the other important changes in the nervous system which are commonly recognized. These results in turn should put us in a position to determine to what extent and in what way this character may be modified.

Although it has long been known that at birth the percentage of water in the central nervous system was much greater than at maturity, yet the change in this character through the life cycle has never been systematically followed, and it thus happens that there are no other extensive records with which to make comparison. The relations of existing data to this investigation will be discussed later on.

The data used for the following study were largely obtained from the same animals which furnished the records employed for the two previous researches on the weight of the brain and of the spinal cord of the albino rat under different conditions of age, body-weight and body-length (Donaldson '08 and '09) although many cases have been necessarily excluded because the percentage of water had not been determined. On the other hand, a few new records have been added to the original series.

In carrying on this work, which has extended through a number of years, I have been greatly assisted by Dr. Hatai, as well as by two of my former students, Dr. Polkey and Dr. Whitelaw, both of whom made a number of the determinations of water under my

directions, and to all of these gentlemen I wish here to express my obligations for assistance.

Technique. The determination of water has been made for the entire encephalon severed from the cord at the level of the first spinal nerve, and for the entire cord, the spinal nerves having been clipped away at their origin from the cord. The rats used were chloroformed, eviscerated and rapidly dissected. No special device for preventing evaporation during dissection was used. The percentage of water applies therefore to the nerve structures proper, surrounded by the meninges and containing such blood as usually remains after the foregoing treatment.

The details of the technique according to which the brain and spinal cord were removed have been already given (see Donaldson '08, p. 346). Each brain or cord was placed in a small glassstoppered weighing bottle, and after being weighed in the fresh state, was dried in a closed water bath which had a temperature ranging from 85°-95° C. and then was cooled in a dessicator over sulphuric acid, and reweighed.

The brain took somewhat longer to dry as a rule than the spinal cord, but usually seven days in the water bath served to bring it to a constant weight. At various times objections have been raised to the determination of the percentage of water by the use of heat. The other method which is most approved is that of drying the material at the room temperature or somewhat above, in a vacuum over sulphuric acid.

A comparison of these two methods has been made for the brain and cord of the rat, but no significant differences have thus far been found. I shall, however, reserve the discussion of the data on which this statement is based for another occasion.

The percentage of water in the brains of albino rats of different body weights. The number of cases is 409 males and 212 females. The mean values for the percentage of water in the brain for given body weights differing by 10 grams, as determined by a correlation table, are entered in table 1.

The examination of table 1 shows for the brain a relative loss of water amounting to about ten units between birth (body weight 5 grams) and the end of the series. This loss is most