SCIENCE. 



161 



and supporting the brain with the fingers or a bit of cot- 

 ton. Then transfer to the bowl of alcohol as above di- 

 rected, and the increase in weight will represent, with 

 approximate accuracy, the weight of the brain. 



Removal of the pia. — This is most easily ac- 

 complished at the time of the removal of the brain to the 

 stronger alcohol. At any subsequent period the pia is 

 apt to be more firmly adherent. If the brain has been 

 allowed to dry at all during its removal from the skull, 

 the pia comes off with great difficulty. 



Instruments and materials. — Forceps ; fine forceps ; 

 medium scissors; wetting-bottle of 15 p. c. glycerine; 

 cotton thoroughly wet with water, and so moulded as to 

 form a sort of shallow cup in which the brain may rest 

 without danger of rolling off. 



Place the brain upon the cotton, and wet it with the 

 glycerine. Then let it rest upon its ventral side, and 

 grasp it in the cotton, firmly yet gently. Grasp with the 

 forceps the fold of pia which occupies any one of the 

 fissures, especially at the point of forking or junction with 

 another fissure, and pull along the line of the fissure. 

 Usually the fold of pia will come out easily, and with it 

 will be removed some of the pia covering the free surface 

 of the gyri between it and the adjoining fissures. Pro- 

 ceed thus until the pia has been removed from the dorsal 

 and lateral aspects of the hemispheres. Avoid pulling 

 across the line of the fissures. The larger forceps are 

 easier to work with, and less apt to puncture the brain ; 

 but the fine forceps are sometimes required for the re- 

 moval of the pia from the bottom of a deep fissure. The 

 caudal surface of the hemispheres may be reached by 

 slightly ventriducting the cerebellum. The mesal pia 

 can only be removed close to the margins of the hemis- 

 pheres. 



On one side, preferably that on which the N. opticus 

 was cut shorter, raise the mass of nerves formed by the 

 divisions of the N. trigeminus and N. abducens, by its 

 lateral border, and cut with the scissors the N. oculomo- 

 torius which holds the mesial border close to the brain. 

 This will permit the mass to be turned caudad so as to 

 expose the course of the slender N. trochlearis which 

 emerges from between the hemispheres and the cerebel- 

 lum. It also permits the removal of the pia fiom the 

 region just laterad of the hypophysis. Grasp the pia on 

 the ventrimeson just caudad of the Bulbi olf., and pull 

 caudad so as to remove it as far as the chiasma, taking 

 care not to tear the delicate terma just dorsad of the 

 chiasma. Then remove the pia from the olfactory tracts. 



In removing the pia from the medulla the position of 

 the nerve roots should be constantly kept in mind, and 

 the traction should be laterad and cephalad. One of the 

 most difficult things is to preserve uninjured the series 

 of roots of the N. hypoglossalis, for their connection with 

 the pia seems to be closer than with the medulla. 

 Sometimes it may be necessary to let the brain be wholly 

 below the surface of water or alcohol so as to float the 

 roots out, and render them more apparent. 



As suggested on a previous page, it is often as well to 

 leave the roots longer on one side than the other, but the 

 choice may be determined mainly by the degree of suc- 

 cess in the various operations which have been described. 



If desired, later numbers of " Science " will contain di- 

 rections for the general dissection of the brain. Mean- 

 time, it would be well for the student to make outline 

 drawings of the brain he has prepared, especially of its 

 base. Most of the principal features of this surface can 

 be identified from the figure of the corresponding surface 

 of the human brain to be found in any good Human 

 Anatomy. The drawing should be enlarged two diam- 

 eters, and the brain should be kept wet with the glycer- 

 ine mixture, while it is out of the alcohol. 



LIST OF WORKS AND PAPERS REFERRED TO. 



Chauveau, A. — A. Traite d Anatomie Comparee des 

 Animaux Domestiques, 2d edition, O., Paris, 1871. 



Dalton, J. C.— . Centres of Vision in the Cerebral 

 Hemispheres. Med. Record, March 26, 1881. 337-339, 

 2 figures. 



Flower, W. H. — . Observations on the posterior 

 lobes of the cerebrum of the Quadrumana, with a de- 

 scription of the brain of a Galago. Phil. Trans., 1862, 

 185-201 ; 2 plates. 



Foster Langley. — A. A Course of Elementary In- 

 struction in Practical Physiology. 3 edition, D., pp. 276, 

 London, 1878. 



Sanderson, J. B. (Editor). — A. Hand-Book for the 

 Physiological Laboratory. 8vo., text, pp. 585 ; Atlas, 123 

 plates. Phil. 1873. Reprint of the English edition with 

 slightly different paging. 



Straus-Durckheim, H.—B. Traite Pratique et Theor- 

 etique d'Anatomie Comparative, Comprenant l'Art de 

 Dissequer les Animaux de toutes les Classes et les Moy- 

 ens de Conserver les Pieces Anatomiques. 2 vols., L). 

 870 pages, 4 plates, Paris, 1842. 



Wilder, B. G. — 9 . A Partial Revision of Anatomical 

 Nomenclature, with Especial Reference to that of the 

 Brain. "Science," II, 122-126 and 133-138, March 19 

 and 26, 1 88 1. 



ATOMS AND MONADS, THEIR METAPHYSICAL 

 DEVELOPMENT. 



By Dr. Diodato Borrelli. 



(Translated from the Italian by the Marchioness Clara Lanza.) 



In previous chapters of this work 1 it has been shown 

 that the whole product of our psychological activity 

 typifies a purely metaphysical world. It has likewise 

 been seen, that the vast compound of forms by means 

 of which exterior nature is represented to us, is not an 

 extrinsic reality, but merely our own impressions, the 

 result of slow and unconscious practice. A minute 

 physio-psychological analysis leads us to this necessary 

 conclusion. Colors are mere modifications, induced in 

 certain groups of ganglion and cephalic cells by a stimu- 

 lus which acts upon the organs of sight. Sounds are 

 another form of cellular modification determined by 

 a different kind of stimulus. Weight and resistance are 

 phenomena of muscular sense. Form and size, synthetic 

 relations, and therefore purely subjective phenomena. 

 All the complex qualities by means of which physics are 

 able to recognize different bodies, are nothing more than 

 our own determinations. From this we may properly 

 conclude that body and matter are not extrinsic realities, 

 but a complication of modifications produced within us 

 by exterior impulses. 



Our world is therefore purely phenomenal, and not a 

 reality. Herbart reasonably maintains that the first 

 moment of research must necessarily be one of doubt, 

 or scepticism, which is degraded or elevated in propor- 

 tion as the uncertainty concerns things as they seem to 

 us, or whether it relates to existence itself. Does the 

 reality exist ? This is the first question which presents 

 itself to the philosopher. And it it does exist, what con- 

 stitutes it and the consecutive research ? " We cannot 

 deny the reality," says Herbart, " because, to do so, is to 

 remove all possibility of the phenomenal world before 

 mentioned. Sensations, representations and thoughts 

 would be completely annulled." 



This phenomenal world, resulting from the data of ex- 

 perience, is that which induces us to admit the existence 

 of positivism. But these data do not constitute real 

 existence, because they are not self-subsisting, but de- 

 pend upon something else. That is to say, they exist in 

 something else and by means of something else. Actual 

 existence does not admit of either relation or dependence, 

 it is based upon itself, and is, therefore, an absolute con- 



1 Borrelli. Vita E Nattira. Studii sui temi piU important! del 

 Moderno Naturalismo. Naples, 1880. 



