SCIENCE. 



man, we find that successively the caiidalus, the lenti- 

 cular is and the claustrum become differentiated from a 

 common gray mass continuous with the cortex at the 

 base of the cerebrum. 



I would add in regard to the term Cortex that the 

 Optic lobes 3 ' 6 and the Rhinencephalon 5 exhibit the corti- 

 cal structure as the cerebrum and the cerebellum. 



The following terms not included in Prolessor Wilder's 

 series, are submitted, and for them I invite the severest 

 criticism. Some of them are established by others. 



Cappa (cinerea r ) — The gray cap covering the Oplici, 

 well developed in most mammalia, rudimentary in man. 



Ectothalamus*. — The outer gray thalamic zone. 



Entothalamus*. — The inner gray thalamic zone. 



Intercrurale*. {Ganglion). — Ganglion Interpedun- 

 cular e 3 > 4 . 



Sigma*. — The S shaped involution of the nerve- 

 cell layer of the cortex which constitutes the basis of the 

 Hypocompa. 



Nucleus trapezii*. — The superior olive. The 

 development of this body seems to bear an inverse re- 

 lation to that of the true olive. In man the olive proper 

 is highly developed, in the cat poorly — in the latter the 

 nucleus of the trapezium is well marked and folded ; in 

 man it is ill-marked. 



Oblongata*. — The post-pontinal area of man ; the 

 medulla oblongata. 



Stride*. — The stria medullares alba of the founh 

 ventricle. 



Velum cerebelli*. — The valve of Vieussens ; this is 

 the true embryonic starting point of the Cerebellum. 

 The velum medullare ant erius. 



Velum oblongat.-e*. — The velum medullare pos- 

 terius. It arises from the interna'l division of the post 

 pedunculus in its oblongata portion, and covets the pos- 

 terior part of the fourth ventricle. 



Velum FLOCCULI*. — The velum medullare inferius. 



GRACILIS* {Funiculus). — Funiculus gracilis, contin- 

 uation of corresponding column in cord ; part of the 

 posterior pyramids. 



Cuneatus* {Funiculus). 



Tuberis* {Funiculus). — Funiculus of Rolando; the 

 columnar fi-ld containing the Tuberculum of Rolando. 

 There is a lobulus tuberis, which is otherwise provided 

 for. 



Nodi*. — Two symmetrical eminences, situated each 

 in the shallow depression bounded by the opticus, thal- 

 amus and habena, probably corresponding to the gang- 

 lion habena (Gang I. habenula*). There is a notable 

 large opening cephalad of these eminences, which re- 

 sembles the openrng under the taenia containing the 

 vein which gives the latter its bljish color. I can find 

 no notice of this opening anywhere. The eminences are 

 represented obscurely in Fig. 70 of Ilenle' 3 . 



Decussatio Fontinalis.** — Fontanen artige Hau- 

 benkrenzung. 5 



In conclusion, I would urge the adoption of some briet 

 arbitrary affix or prefix in place of the words commis- 

 sure and ganglion. He who limits himself to a study of 

 surface contours will not appreciate the absence of 

 such abbreviations as much as he who is compelled to 

 wade through the labyrinth of the internal cerebral struc- 

 ture. 



Gris for ganglion would perhaps do ; thus Grishabena, 

 Gristegmentum, Grisfastigium for Ganglion habena;, 

 Ganglion and Nucleus tegmenti, Nucleus fastigii. The 

 term nucleus is a very unfortunate one as it has another 

 and very different meaning, which in my experience as 

 a teacher of cerebral anatomy, has led to confusion in 

 the mind of every beginner. Professor Wilder, who ap- 

 pears to be as much at home in etymology as in cerebral 



♦Terms proposed by myself, not to be found in previous publications. 

 ** A single affix or prefix might be devised in place of decussatio, or 

 fontidecussatio, pinidecussatio,/>yridtcussatio f 



anatomy, will solve these problems no doubt better than 

 I could pretend to. 



references. 



1. Wilder, B. G. A partial revision of anatomical 

 nomenclature with especial reference to that of the 

 Brain. " SCIENCE " Nos. 38, 39. 



2. Henle. Nervenlehre, p. 1 18. 



3. Forel. Untersuchungen uber die Hauben Region, 

 Arch, fur Psychiatric VII. 



4. Gudden. Ibidem, X. 



5. Meynert. Vom Gehirn der Saugethiere. Strieker's 

 Handbuch II. p. 724, line 11 from bottom. 



6. Spitzka. The higher ganglia of the mid and hind 

 brain. Journal of Nervous and Mental Diseases. July, 

 1880. (Designation of figure 10.) 



7. Schwalbe. ( Hoffmann-Schwalbe), quoting Tartu- 

 feri. Gazetta medica Italiani. Serie VIII". Tom. III. 

 and Rivesta sperimcntale, 1 878. 



New York, 130 East 50th street. E. C. SPITZKA. 



HOW DOES GRAVITY CAUSE MOTION ? 



To the Editor of " SCIENCE :" 



The interesting article by Mr. E. L. Larkin in 

 "Science" for March 26, on the Interrelations of Gravity, 

 Hea>, Motion, etc., induces me to offer you some thoughts 

 on the subject, with the hope that I may throw light 

 upon it from another point of view. There is one widely 

 accepted doctrine of modern physics which I confess I 

 could never understand, that of Potential Energy. It may 

 serve as a convenient explanation of the mysteries of fal- 

 ling force to say that energy may be at one time motion, 

 and at another time the possibility of becoming motion. 

 The rule explains the problem, but what explains the 

 rule? Can motion become anything else than motion? 

 Can it now convert itself into Rest, into Gravity, into 

 Potentiality, or into anything else than simply motion ? 

 Is it not, like force and matter, an unvarying infinitude 

 of the universe ? 



Motion means simply the translation of substance 

 through space, and it possesses a fixed energy dependent 

 upon the weight of the substance and the speed of the 

 translation. If the portion of substance moved be a min- 

 ute portion of matter, either forming an elementary con- 

 stituent of a solid mass, or a separate molecule of a gas, 

 we call its motion heat ; and the result of its impact 

 with exterior particles, temperature. If it be a mass of 

 such particles its translation should be particularized as 

 mass motion. In addition to these modes of motion, 

 Electricity and Magnetism must also be considered as 

 more special modes of motion, uuless we admit the pos- 

 sibility of motion becoming something else, and this 

 something else again becoming motion. 



Can we admit this ? What does terrestrial gravity 

 teach us ? If gravity is convertible into motion, then we 

 have reason to conclude that the gravity should disappear 

 as the motion increases. The law of gravitation asserts 

 that the action of the earth and of a falling body are ne- 

 cessarily reciprocal. Tne earth must fall towards the 

 body with the same energy that the body displays in 

 falling towards the earth. The body, then, can not de- 

 rive its energy of fall from the earth, unless we claim 

 that the earth derives its energy of fall from the body. 

 Such a cross-lending of force is inadmissable. The 

 energy displayed by the body must come from itself, not 

 from the earth. It is not a transformation of the earth's 

 gravity into motion. Is it a transformation of its own ? 

 This we cannot admit, since the body loses no gravity. 

 It cannot well give and keep at the same time. The 

 body falls 16 feet in the first second, and ends with a 

 velocity of 32 feet per second. This 32 feet per second 

 is a positive momentum, and must continue until over- 



