impulses which we think it is feeling. In other words we must use every means to ascertain the mental factors of the situation before offering any interpretation of the meaning of the behavior, or using the observed behavior to strengthen any particular theory of psychic functional relations We cannot hope for absolute certainty of the processes in other minds by any known method, and the certainty is less the further we recede from ourselves. But the careful student of the habits of the animal in its natural condition, by exercising care to have the animal in as nearly natural conditions as the experimental necessities admit of, and by being careful to isolate the experimental condi tions for the animal, will be able to interpret the movements and incipient movements in mental terms and thus have a close approximation to accuracy in grading the intelligence of the animal as shown in the particular situation. Accurate and detailed knowledge of the natural life of the animal, it cannot be insisted too strongly, is of the highest importance both for the proper planning of experiments and for the interpretation of the results.

If under these conditions it can be shown that an animal now has a grade of intelligence sufficiently high to serve as the guide in shaping any and all of the instinctive modes of behav ior with which it is equipped, it has not been shown thereby, of course, that intelligence was the means of its development. The development of mind may have brought fourth this grade of intelligence at a later stage in the race history than that at which the instincts took their rise. In this case the results would be merely negative. If, though, it can be shown that a given animal has, as its mental equipment, an intelligence too low to deal with a situation as complex as that dealt with by the instinct, the inference is then clear that the instinct has come by some other way than by intelligence. For our major premise, as before, is that intelligence as a whole never retrogrades, but when released through automatization proceeds to greater complexity and higher organization through dealing with more complex situations. This case would presuppose a retrograding and would therefore be impossible. And so it was not con

scious (I do not mean self-conscious) choice which determined originally the mode of reaction which is now instinctive.

This position being established, the way would then be open for the psychologist to construct and maintain a theory of the origin of volition and cognition as developing out of a system of organic behavior. This negative evidence, if it can be found, will contribute to a constructive theory of the systematic development of mind as a progress from the simpler and less organic to the higher and more organic. For intelligence is both of these as compared with instinct.

T. H. HAINES.

A REVIEW OF SOME RECENT LITERATURE ON THE CHEMISTRY OF THE CENTRAL NERVOUS SYSTEM.

By ISADOR H. CORIAT, M.D.,

Worcester Insane Hospital.

The last few years have witnessed a marvelous impetus and great evolution in our ideas of anatomical and chemical facts concerning the central nervous system. The cerebro-spinal fluid has also shared in this advance, partly as the result of independent study, but chiefly because of its intimate relation to the nerve structures. The literature on the subject is scattered through the various journals and reports, but outside of THUDICHUM's book on the chemical constitution of the brain of man and lower animals, and of SICARD'S recent work on the cerebro-spinal fluid, there has been no serious attempt to summarize the recent publications on the chemistry of the nervous system, both in normal and pathological states. It seems opportune, therefore, to review the most available facts along these lines, and point out in what manner these may be utilized to stimulate further research. Of course, in the limits imposed by a review, only the most important papers can be abstracted. The work on neuro-chemistry has been pushed in several directions, of which the principal ones merit the following subdivisions:

1. More systematic attempts at classifying the various substances of the brain.

2. The isolation of nerve products by newer methods.

3. The further ultimate analysis of these products.

4. The chemistry of the finer structure of the nerve cells, including the micro-chemistry of various stains.

5. The autolysis of brain tissue.

6. Analysis of the brain and cord in various normal and pathological states.

7. The chemistry of the cerebro-spinal fluid, particularly as a medium for the various products of nerve degeneration.

8. The physiological action of various normal and pathological nerve products.

The substances so far isolated from the brain follow. The classification is merely a tentative one and must not be looked upon as

final. It is partly adopted from THUDICHUM and KOCH and partly the result of my own observations.

A. Water.

B. Proteids.

1. A globulin coagulating at 47°-56° C.

2. A globulin coagulating at 70° C.

3. Neuroglobulin, coagulating at 45°-50° C.

(According to HALLI

BURTON it is the coagulation of this substance in the nerve cells, which is the physico-chemical cause of death from hyperpyrexia).

4. Neurostromin (in traces).

5. Nucleo-proteid (LEVENE, HALLIBURTON, SCHKARIN).

6. Neurokeratin (KÜHNE and CHITTENDEN).

7. Albumoses and Peptones.

C. Extractives.

1. The purin bases of the nucleo-proteids (Adenin, guanin, hypoxanthin).

2. Pyramidin bases (thymin and cytosin).

3. Amido-acids (leucin and tyrosin).

4. Urea (also a normal constituent of the cerebro-spinal fluid).

D. Carbohydrates.

1. Inosite.

2. An unknown carbohydrate which gives the furfurol reaction and is

probably related to the pentoses.

3. Galactose (a split-product of cerebrin).

4. Dextrose (in the cerebro-spinal fluid)-CORIAT.

5. Pyrocatechin (in the cerebro-spinal fluid ?)-HALLBURTON.

3. Lactic acid (optically inactive ethylidene lactic acid. This is the result both of post-mortem decomposition and of long continued activity in the central nervous system, as in convulsive seizures. In both cases, the acid passes into the cerebro-spinal fluid).

4. Glycerophosphoric acid (a decomposition product of lecithin).

5. Formic acid.

6. Acetic acid.

7. Succinic acid.

8. Stearic, oleic acid, palmitic acids (decomposition products of lecithin).

9. Litho- and Butophosphoric acid (THUDICHUM).

F. In Pathological Conditions.

1. Cholin (a decomposition product of lecithin-MOTT and HALLIBURTON, DONATH, WILSON, CORIAT).

2. Neurin.

3. Uric acid.

4. Kreatin.

5. Trimethylamin (a post-mortem product).

6. Neuridin.

G. Inorganic bodies. Sodum, potassium, ammonium, calcium and iron, present either as dissociated ions, or in organic combination. The radicles Cl, SO, PO1, and CO, are also present as disociated ions or with the cations above mentioned.

H. Lecithins (Monophosphatids containing one nitrogen molecule in the proportion N:P 1:1). The various lecithins from eggs, barley, malt, yeast and brain show variations in the amounts of phosphorus and in the methyl content.

1. Lecithins (Stearylolely, margeryloleyl, palmityloleyl).

2. Amido-lecithins (amido-myelin). Contains two nitrogen molecules N;P=2:1.

Cerebrin phosphoric acid (BETHE)

J. Cholesterin (occurs both free and in the form of an ester).

K. Sulphur compounds (Cerebusulphatides and sulphatids of THUDICHUM). L. Amido-fats (Krinosin and Bregenin).

As a contrast, THUDICHUM'S classification alone should be consulted (Die chemische Konstitution des Gehirns des Menschen und der Tiere, pp. 89-91), and the reader will also find there a minute discussion of these various products, with particular relation to their chemical reactions.

It is unnecessary to enter here into the details of the newer methods for the isolation of the various brain substances. The original papers must be consulted, of which reference is given in the bibliography affixed to this review. It suffices to mention THUDICHUM'S complete isolation methods, the acetone method of KOCH for the separation of lecithin, kephalin and cerebrin, LEVENE'S methods for the isolation of nucleic acid and the nucleo proteids, KocH's modification