SCIENCE. 



75 



tions, produce a known quantity of electricity, or which 

 would charge a condenser of one microfarad capacity to 

 a given potential. Knowledge as to the power of a gal- 

 vanic battery was much more definite. Everything in 

 that respect could be stated with exactitude. If knowl- 

 edge of the practical uses of electrical machines were 

 comparable with that in respect to the galvanic battery, 

 knowledge as to the efficiency of the former would soon 

 be equally definite. The necessity of proper standards 

 based on numerical data was understood in more than 

 one branch of physics; but the present remarks were di- 

 rected only to electricity, which had in recent years un- 

 dergone almost a complete transformation. After de- 

 scribing the principles upon which a system of electrical 

 measurement should be founded, the steps taken by Ohm, 

 Weber, Oersted, and others, in arriving at definite laws, 

 were related and tabulated for comparison. Weber's 

 system had been extended by Sir W. Thomson, and the 

 praciical applications of electricity in its early days pro- 

 duced the necessity of being able to express results upon 

 a coherent system of standard units. For that purpose 

 the committee of the British Association on electrical 

 standards was appointed, and the B. A. unit resulted. 

 The data upon which that unit was founded had subse- 

 quently been verified, and at the present time a redeter- 

 minat'on of its accuracy was about to take place. The 

 absence of any standard resistance coils was pointed 

 out, and the suggestion made that it would reflect credit 

 on the Society if it at once set to work with the view of 

 establishing a definite standard resistance, with which in- 

 struments used for every-day practical purposes could be 

 occasionally verified and adjusted. A paper on " Some 

 Experiments on Induction with the Telephone," by Mr. 

 A. W. Heaviside, was then read. In the discussion 

 which followed. Prof. Hughes, Mr. Stroh, Prof. Ayrton, 

 and others took part. 



FURTHER NOTES ON-THE BRAIN OF THE 

 IGUANA AND OTHER SAUROPSID^. 



By Edward C. Spitzka, M. D. 



I would add to the observations published in No. 7, 

 Vol. I. of Science, relating to the brain of the Iguana, 

 the following: 



1st. The ganglionic intumescence upon the inner edge 

 of the cerebral hemisphere, which I supposed to repre- 

 sent the homologue of the molecular basis of the 

 Fascia dentata of Tarini in the mammalia, is more volum- 

 inous in the middle of the hemispheric length, than in 

 the posterior third. The homologization of the entire 

 inner wall of the hemisphere with the Comic Ammonis 

 of mammals gains strength from the fact that in the 

 Opossum the Cornu Ammonis extends almost along the 

 whole inner hemispheric wall, and is but slightly folded 

 as compared with that of the Rodentia. That the eleva- 

 tion which I supposed to correspond to the fascia dentata 

 and tanzola cinerea, might be interpreted as one of the 

 thalamic tubercles, which I considered an open question 

 at the time of my writing the first commmunication, and 

 which I now hold to be disposed of definitely as well as 

 the other supposition. 



2nd. There is a molecular accumulation at the base of 

 the cerebral hemisphere, in the common basilar gray, 

 and beneath the elevation of the corpus striatum, which 

 may correspond to the lenticular nucleus. 



3rd. At and above the level of the emerging third pair 

 of nerves, there is a beautiful nucleus of large multipolar 

 cells, resembling the cells of the auditory nucleus (that is 

 of the large celled division of that nucleus) in contour and 

 in dimensions. This cell group in its situation corre- 

 sponds to the nucleus tegmenti of mammals. I would 

 here note that throughout the animal range, the cells of 

 the nucleus tegmenti and the special division of the audi- 

 tory nucleus referred to seem to keep step in development. 

 This fact would add another link to the chain of evidence 



attempted by Meynert, who surmised that an auditory 

 tract passed through the cerebellum to the brachium 

 conjunctivum, (and therefore through this cell group) on 

 its way to higher projecting fields. 



4th. The so-called nucleus dentatus of the cerebellum, 

 which should be termed simply nucleus cerebelli, since it 

 is not dentated even in all the mammalia, is clearly pres- 

 ent in the cerebellum of the Iguana. It can be found at 

 the junction of the cerebellar peduncles with the main 

 cerebellar mass, and consists of well marked cells of 

 moderate dimensions. 



5th. The " fasciculus from the habenulas to the teg- 

 mentum " so-called by Meynert, but which Gudden and 

 his pupils correctly state to run from the habenulae to 

 the ganglion interpedunculare, has not been yet identi- 

 fied in animals lower in rank than the mammalia. I find 

 it well-developed occupying exactly the same relations 

 and presenting the same histological peculiarities as with 

 mammals in the Iguana. 



6th. The fourth pair does not reach the valve of Vieus- 

 sens in levels lower than those in which the root has its 

 origin, as in the turtle (Nanemys guttatus, Chelydrd) 

 and the mammalia, but distinctly arises in the same level 

 in which it reaches the valvule where it decussates. 

 The nerve itself, however, emerges in levels superior to 

 the latter. 



7th. While the cells of the oculomotoriotrochlearis nu- 

 cleus, and those of part of the auditory origin are of large 

 dimensions, those of the abducens, facial, and motor- 

 trigeminal origin are remarkably small. The reduction 

 in size of the cells is as might be inferred accompanied by 

 a reduction in size of their nuclei. This fact suffices to 

 dispose of the recently advanced claims, that motor cells 

 have larger nuclei than sensory ones. The reduction in 

 size of these motor groups and their presenting such a con- 

 trast to the great development of the cells in other motor 

 groups in the Iguana, has to my mind much of the enig- 

 matical. The largest cells in the nervous system of the 

 Iguana, are the multipolar cells of the reticular field, 

 (my ganglion reticular e in mammals) those of the aud- 

 itory origin and nucleus tegmenti are of the same or 

 nearly the same dimensions. 



8th. The mesencephalic nucleus of the fifth pair is 

 represented as in other reptiles by round cells, sunk in 

 the niche between the two optic lobes; they are not spread 

 out on the contour of the central tubular grey, ss in 

 mammals, but concentrated more at the median line. 

 Some of the cells can be identified beneath the mter-op- 

 tic lobes. 



9th. The cells of the substantia ferruginea of man are 

 represented by a group of numerous small ganglionic 

 I bodies, whose connection with the fifth nerve is clearer 

 than in the mammalia. 



10th. The auditory nerve fibres send a powerful strand 

 which decussates with its fellow in the raphe. In its 

 course each strand traverses or circumscribes the poste- 

 rior longitudinal fasciculus. This same strand is found in 

 the mammalia, but in the latter it is deeply seated ; in the 

 Iguana it is more superficial, and the erroneous inference 

 might be drawn that this strand in the reptile is equiva- 

 lent to the striae acusticioi mammals. The latter are 

 however, absent in reptiles, and although in some species 

 visible eminences are formed at the floor of the fourth 

 ventricle, crossing at right angles the long'tudinal emi- 

 nences of the posterior longitudinal fasciculi ; these are 

 the homologues of the more anterior and concealed part 

 of the auditory decussation of mammals. 



nth. In no reptile have the nuclei of the columns ot 

 J Goll and Burdach been identified. In the Iguana I can 

 I readily identify them, although much smaller than the 

 corresponding nuclei of the mammalia. Their demarca- 

 tion is, however, distinct. 

 I 12th. In the Iguana as in the turtle there is an accu- 

 I mulation of numerous multipolar cells at the raphe in the 



