Зображення сторінки
PDF

March 24, 1892.

Mr. JOHN EVANS, D.C.L., LL.D., Treasurer and Vice-President,

in the Chair.

The Right Hon. Spencer Compton Cavendish, Duke of Devonshire, was admitted into the Society.

A List of the Presents received was laid on the table, and thanks ordered for them.

The Croonian Lecture was delivered as follows :—

Cuooniax Lecture.—"The Temperature of the Brain, especially in relation to Psychical Activity." By ANGELO Mc-sso, Professor of Physiology in the University of Turin. Received March 24, 1892.

(Abstract.)

In his investigations on the temperature of the brain the author has employed, in preference to the thermo-electric pile, exceedingly sensitive mercurial thermometers, constructed specially for the purpose. Since each thermometer contains only 4 grams of mercury, the instruments respond very rapidly to changes of temperature, and a change of not more than 0t002° C. can easily be measured by means of them. The author has studied the temperature of the brain, comparing it with that of arterial blood, of the muscles, of the rectum, and of the uterus; his observations were made on animals under the influence of morphia or various anaesthetics, and also on man.

The curves of the observations made show that in profound sleep a noise, or other sensory stimulus, is sufficient to produce a slight development of heat in the brain, without the animal necessarily awakening.

In profound sleep the temperature of the brain may fall below that of the blood in the arteries. This is due to the very great radiation of heat which takes place from the surface of the head.

The brain when subjected to the action of the ordinary interrupted current rises in temperature. The rise is observed earlier in the brain than in the blood, and the increase is greater in the brain than in the general blood-current or in the rectum. During an epileptic seizure brought on by electrical stimulation of the cerebral cortex, the author observed within twelve minutes a rise of 1° C. in the temperature of the brain.

As a rule the temperature of the brain is lower than that of the rectum; but intense psychical processes, or the action of exciting chemical substances, may cause so much heat to be set free in the brain that its temperature may remain for some time 0'2° or 0'3° C. above that of the rectum.

When a dog is placed under the influence of curare, the temperature of the brain remains fairly high, while that of the muscles and that of the blood falls. The difference of temperature thus brought about is great and constant. 'In one instance, the temperature of the brain was l-6" C. above that of the arterial blood in the aorta. Such observations warn us not to regard the muscles as forming, par excellence, the thermogenic tissue of the body.

In order to show how active are the chemical processes in the brain, it is sufficient to keep the animal in a medium whose temperature is the same as that of the blood. When the effects of radiation through the skull are thus obviated, the temperature of the brain is always higher than that of the rectum, the difference amounting to 0'5° or 0-6° C.

Observations made while an animal is awake tend to show that the development of heat due to cerebral metabolism may be very considerable, even in the absence of all intense psychical activity. The mere maintenance of consciousuess belonging to the wakeful state involves very considerable chemical action.

The variations of temperature, however, observed in the brain, as the result of attention, or of pain or other sensations, are exceedingly small. The greatest rise of temperature observed to follow, in the dog, upon great psychical activity was not more than 001° C. When an animal is conscious, no change of consciousuess, no psychical activity, however brought about experimentally, produces more than a slight effect on the temperature of the brain.

The author shows an experiment by which it is seen that, as part of the effect of opium, the brain is the first organ to fall in temperature, and that it may continue to fall for the space of eighteen minutes, while the blood and the vagina are still rising in temperature.

The author discusses the elective action of narcotics and anaesthetics. He shows that these drugs suspend the chemical functions of the nerve-cells. In a dog rendered completely insensible by an anaesthetic, one no longer obtains a rise of temperature upon stimulating the cerebral cortex with an electric current. These results cannot be explained as merely due to the changes in the circulation of the blood. The physical basis of psychical processes is probably of the nature of chemical action.

In another experiment, in an animal rendered insensible with chloral, the curves of temperature show that when the muscles of a limb are made to contract, the temperature of the muscles rises, but falls rapidly as soon as the stimulation ceases, soon returning to the normal. This is not the case, however, with the brain excited by an electric current. Here the stimulus gives rise to a more lasting production of heat; the temperature may continue to increase for several minutes after the cessation of the stimulation, indeed often for half an hour. This may possibly explain why, upon an electric stimulation of the cerebral cortex, the epileptiform convulsions are not immediately developed, but only appear after the lapse of a latent period of several minutes.

This experiment may be made to show the elective action exercised upon the brain by stimulant remedies. The injection of 10 centigrams of cocaine hydrocblorate produces a rise of temperature in the brain of 0'36° C., without any change in the temperature of the muscles or of the rectum being observed. In a curarised dog, the intervention of the muscles being thereby excluded, the action of the cocaine may produce a rise of as much as 4° C. in the temperature of the brain, the author having observed a rise from 37° to 41° C. This shows that in arranging the calorific topography of the organism a high place must be assigned to the brain.

The author concludes by expressing the hope that the comparative study, by the direct thermometric method, of the temperature of the various organs of the body will enable us to push forward our knowledge of the phenomena of life.

Presents, March 24, 1892. Transactions.

Belgrade:—Royal Servian Academy. Spomenik. Nos. 10, 12, 13. 4to. Beograd 1891-92; Glas. No. 30. 8vo. Beograd 1891; Jovan Bak: Jedan Biographski Zapis. 8vo. Beograd 1891.

The Academy.

Berlin:—Gesellschaft fur Erdkunde. Zeitschrift. Bd. XXVI.

No. 6. 8vo. Berlin 1891. The Society.

Bucharest:—Societate de Sciinte Fizice. Buletin. An I. No. 2.

8vo. Bucuresci 1892. The Society.

Buenos Ayres:—Museo Nacional. Anales. Entrega 18. 4to.

Buenos Aires 1891. The Museum.

Lausanne:—Societe Vaadoise des Sciences Naturelles. Bulletin.

Vol. XXVII. No. 105. 8vo. Lausanne 1892.

The Society.

Leipsic :—Konigl. Sachs. Gesellschaft der Wissenschaften. Be

richte (Math.-Phys. Classe). 1891. Heft 4. 8vo. Leipzig Transactions {continued).

1892; Berichte (Philol.-Histor. Classe). 1891. Heft 2-3. 8vo.

Leipzig 1892. The Society.

London :—Royal Medical and Chirurgical Society. Medico-Chir

urgical Transactions. Vol. LXXIV. 8vo. London 1891.

The Society. Royal United Service Institution. Journal. Vol. XXXVI.

No. 169. 8vo. London 1892. The Institution.

Paris :—Faculte des Sciences. Theses presentees pendant l'Annee

1891. 8vo and 4to. Paris 1890-91. The Faculty.

Prague :—Konigl. Bohmische Gesellschaft der -Wissenschaften.

Abhandlungeu CMath.-Naturw. Classe). Folge VII. Bd. 4.

4to. Prag 1892 ; Abhandlungen (Philos.-Histor.-Philol. Classe).

Folge VII. Bd. 4. 4to. Prag 1892; Sitzungsberichte

(Math.-Naturw. Classe). Jahrg. 1891. 8vo. Prag 1891;

Sitzungsberichte (Philos.-Histor.-Philol. Classe). Jahrg. 1891.

8vo. Prag 1891; Jahresbericht. 1891. 8vo. Prag 1892;

Spisuv, &c. Cislo VI. 8vo. v Praze 1891. The Society.

Washington:—U.S. National Museum. Proceedings. Vol. XIV.

Nos. 880—881. 8vo. Washington 1891-92; Bulletin. Nos.

41-42. 8vo. Washington 1891. The Museum.

Journals.

Astronomy and Astro-Physics. February, 1892. 8vo. Northfield, Minn. The Editor.

Horological Journal. Vol. XXXIV. No. 403. 8vo. London 1892. The British Horological Institute.

Revista do Observatorio. Anno VI. No. 12. 8vo. Bio de Janeiro 1891. The Observatory, Rio de Janeiro.

Revue Medico- Pharmaceutique. Annee V. No. 2. 4to. Constantinople 1892. The Editor. Timehri. Vol. V. Part 2. New Series. 8vo. Demerara 1891. Royal Agricultural and Commercial Society of British Guiana.

Bonneau (H.) and E. Desroziers. Etude sur la Traction Electrique des Trains de Chemin de Fer. 8vo. Paris 1892.

The Authors.

Burdett (H. C.) Burdett's Official Intelligence for 1892. Oblong. London 1892. Mr. Burdett.

Cuervo (E.) Estudio sobre el Sistema Evolucionista. 8vo. Bogota 1891. The Author. Dieterici (Fr.) Alfarabi's Philosophische Abhandlungen. 8vo.

Leiden 1892. The Author.

Fayrer (Sir J.), F.R.S. On Serpent-worship and on the Venomous

Snakes of India. 8vo. London. The Author.

Hehir (P.) Microscopical Observations on the Haematozodn of

Malaria. 4to. Madras [1891]. The Author.

Ricco (A.) Terremoti Sollevamento ed Eruzione Sottomarina a

Pantelleria. 4to. Homa 1892. The Author.

Wolf (R.) Astronomische Mittheilungen. No. 79. 8vo. [Zuric/i]

1892. The Author.

Bronze Medallion, 7 inches diameter, cast in honour of Professor Rudolph Virchow, For. Mem. R.S.

Virchow Testimonial Committee, Berlin.

March 31, 1892.

Mr. JOHN EVANS, D.C.L., LL.D., Treasurer and Vice-President,

in the Chair.

A List of the Presents received was laid on the table, and thanks ordered for them.

The following Papers were read:—

L "An Improved Apparatus for ascertaining the Sensitiveness of Safety-lamps when used for Gas-testing." By Frank Clowes, D.sc. (Lond.), Professor of Chemistry, University College, Nottingham. Communicated by Professor ARMSTRONG, F.R.S. Received March 24, 1892.

An apparatus devised for the purpose of testing the sensitiveness of different forms of miners' safety-lamps, when they are employed for detecting and measuring low percentages of firedamp, has been already described in the 'Roy. Soc. Proc.' (vol. 50, 1891, p. 122).

The section of the apparatus (fig. 1) shows that the apparatus consists of a large cubical wooden box or chamber, into the upper part of which the requisite measured volume of methane or firedamp can be introduced, the complete admixture of this gas with the air of the chamber being then secured by swinging up and down a broad wooden flap, the area of which is nearly equal to the square section oi the chamber.

« НазадПродовжити »