March 27, 1890] 



NA TURE 



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the front surfaces, are fixed against a block of wood, so that the 

 angle between the two surfaces is slightly less than 90°. This 

 simple apparatus will give the interference phenomena produced 

 by means of Fresnel's mirror or bi-prism. — An improved wave 

 apparatus, by John T. Stoddard. This is a method of demon- 

 strating to a class the formation of the compound curves repre- 

 senting the combination of two simple sound waves. — On a 

 recent rock-flexure, by Frank Cramer. — On the origin of the 

 rock-pressure of the natural gas of the Trenton limestone of 

 Ohio and Indiana, by Edward Orton. By the rock-pressure of 

 gas is meant the pressure in a well which is locked in so that no 

 gas can escape ; and the author concludes that the rock-pressure 

 of the gas of the Trenton limestone is due to the pressure of a 

 water column under which it is held in the arches of the rocks. 

 This explanation seems applicable to all gas fields. 



The American Meteorological Journal for January contains 

 a continuation of Faye's theory of storms, and of Ferrel's con- 

 vectional theory of tornadoes, both of which have been already 

 referred to ; the latter paper is concluded in the number 

 for February. Of the other articles in these two months the 

 principal are : — The mathematical elements in the estimation 

 of the Signal Service Reports, by W. S. Nichols. He points 

 out that attempts to measure the accuracy of the daily weather 

 forecasts are liable to give rise to a confusion of ideas, and, con- 

 fining his attention to rainfall, he lays down certain rules for 

 testing the value of the predictions to the community when 

 judged from the stand-points of quantity and quality, as well as 

 the accuracy of the information. — On the use of the "sling" 

 thermometer in the prediction of frosts, by Prof. H. A. Hazen. 

 With the view of protecting delicate plants from destruction by 

 frost, the author advocates the determination of the dew-point 

 in the evening, and if it is found to be as low as 25°, and the 

 air-temperature at 45° or lower, with a clear sky, frost may be 

 expected, and the plants should be protected by smoke from 

 burning straw, before the early morning. — On globular lightning, 

 by Dr. T. C. Mendenhall. The author quotes many interesting 

 instances of this rare phenomenon, the earliest case recorded 

 being at Stralsund in June 1670 ; and he describes several 

 instances in which it has been observed at sea. Photographs of 

 the phenomenon are much wanted. — Diminution of temperature 

 with height, by Prof. PI. A. Hazen. He has recently spent 

 several weeks on the summit of Mount Washington (6300 feet 

 above sea-level), and finds that the diurnal range of tempera- 

 ture, which is very small, is not due to the heating of the air 

 by the sun, but only to the convection currents caused by the 

 warm rocks. The object of the paper is to endeavour to throw 

 light on the true explanation of storm phenomena. — An interest- 

 ing summary, by A. L. Rotch, of the Meteorological Conference 

 held at Paris in September last, in connection with the Interna- 

 tional Exhibition. This is the first general account which has 

 appeared in English. 



SOCIETIES AND ACADEMIES. 

 London. 



Royal Society, March 6. — "On the Development of the 

 Ciliary or Motor Oculi Ganglion." By J. C. Ewart, M.D. 

 Communicated by Prof. M. Foster, Sec. R. S. 



The most conflicting views have for some time been held as 

 to the origin, relations, and homology of the ciliary (motor 

 oculi, ophthalmic, or lenticular) ganglion. By Remak, 

 Schwalbe, Marshall, and others, the ganglion of the ophthal- 

 micus profundus has been described as the ciliary ganglion, and 

 this ganglion has frequently been regarded as the ganglion of 

 the motor oculi nerve, and hence as homologous with the 

 Gasserian and other cranial ganglia. The ciliary ganglion 

 having been shown by van Wijhe to be quite distinct from the 

 ganglion of the ophthalmicus profundus, the old view of Arnold 

 has been recently revived, and already van Wijhe, Hoffmann, 

 Onodi, Dohrn, and Beard have indicated that they regard the 

 ciliary as a sympathetic ganglion. Hoffmann bases his belief 

 on certain observations on the development of the ciliary 

 ganglion in reptiles, while Onodi has adopted this view chiefly 

 because in the higher vertebrates the ciliary ganglion receives a 

 communicating branch from the sympathetic. But Beard, 

 while considering the ciliary a sympathetic ganglion, states 

 that in sharks he has seen nothing in support of " the mode of 



origin for the ciliary ganglion described by Hoffmann," in 

 reptiles. 



In studying the ciliary ganglion in Elasmobranchs I have 

 been specially struck with its tendency to vary not only in the 

 same genus or species, but in the same individual. Of the 

 numerous specimens examined, I have only once found the 

 ganglion entirely absent (in an adult Raia radiata), while I 

 have occasionally (in Acanthias) found two well-developed 

 ganglia on each side. Usually in sharks I found the ganglion 

 lying in connection with the inferior branch of the motor oculi, 

 while in skates it was generally in contact with the ophthalmicus 

 profundus, or lying midway between the motor oculi and the 

 ganglion of the profundus. In form the ganglion varies 

 extremely, rounded or conical in some cases, in others it was 

 represented by two or three groups of cells lying parallel to or 

 in contact with the motor oculi. 



In some cases ganglionic cells had wandered from the gang- 

 lion a considerable distance along the ciliary nerves towards the 

 eyeball. 



Although in sharks the ciliary ganglion often lay in close con- 

 tact with the motor oculi nerve, no ganglionic cells were ever 

 found either in the trunk of that nerve or on any of its branches. 

 In skates the ganglion was usually more intimately related with 

 the ophthalmicus profundus than the oculo-motor. In all cases 

 the ciliary ganglion had at least two roots, one from the motor 

 oculi, and one or two from the ophthalmicus profundus. In 

 skates the profundus root always proceeded directly from the 

 profundus ganglion, and the profundus ganglion was frequently 

 found to be connected by a communicating branch with the 

 Gasserian ganglion. 



Both in sharks and skates, in addition to the ciliary nerves 

 from the ciliary ganglion there were ciliary nerves proceeding 

 from the ganglion and from the trunk of the profundus, and in 

 some cases large ganglionic cells had wandered from the pro- 

 fundus ganglion along the ciliary nerves ; occasionally a few 

 large cells had migrated some distance along the main trunk of 

 the profundus. In all cases the majority of the cells of the 

 ciliary ganglion were only about half the size of the cells of the 

 profundus ganglion. 



In skate embryos under two inches in length no indication of 

 the ciliary ganglion was discovered, and in shark embryos about 

 ten inches in length the ganglion was frequently represented by 

 small groups of cells in the vicinity of the inferior branch of the 

 oculo-motor nerve. In sharks the first steps in the development 

 of the ganglion were not observed, but in skates it was possible 

 to make out all the stages. The first indication of the ganglion 

 was in the form of a slender outgrowth from the inferior border 

 of the large ophthalmicus profundus ganglion, which met and 

 blended with fibres from the descending branch of the motor 

 oculi. The outgrowth from the profundus ganglion was crowded 

 with cells ; the fibres from the motor oculi, like its root and 

 trunk, were absolutely destitute of cells. At a somewhat later 

 stage the cells had accumulated at the junction of the outgrowth 

 from the profundus ganglion with the fibres from the motor oculi. 

 It looked as if the blending of the two sets of fibres had formed 

 a network which resisted the further migration of the ganglionic 

 cells. In typical cases, at a still later stage, all the ganglionic cells 

 had left the outgrowth from the profundus ganglion to form a 

 rounded mass from which the ciliary nerves took their origin. In 

 some cases some of the fibres which connected the profundus gang- 

 lion with the Gasserian seemed to reach and end in the ciliary 

 ganglion. It thus appears that the ciliary ganglion stands in the 

 same relation to one of the cranial nerves (the ophthalmicus 

 profundus) as the sympathetic ganglia of the trunk stand to the 

 spinal nerves, and that the ciliary ganglion may henceforth be 

 considered a sympathetic ganglion. Further investigations may 

 show that the ganglia in connection with the branches of the 

 trigeminus (fifth) nerve may also be considered as belonging to 

 the sympathetic system. In conclusion, I may say that I have 

 found the vestiges of the ophthalmicus profundus ganglion in a 

 five-months human embryo lying under cover of the inner 

 portion of the Gasserian ganglion, and satisfied myself that the 

 ophthalmicus profundus of the Elasmobranch is represented in 

 man, as suggested by several writers, by the so-called nasal branch 

 of the ophthalmic division of the fifth. To as far as possible 

 clear up the confusion that has arisen from mistaking the 

 ophthalmicus profundus nerve for a branch of the oculo-motor 

 or of the trigeminus nerve, and the ganglion of the ophthalmicus 

 profundus for the ciliary ganglion, it might be well in future to 

 speak of the profundus as the oculo-nasal nerve and its ganglion 

 as the oculo-nasal ganglion. 



