Feb. 19, 1874J 



NATURE 



>05 



Till you'd almost think they'd been and caught the devil in the 



trawl ; 

 The tiawl's for fancy drugin' and the work's about the same, 

 Tlie only diff'rance I can see is that wot's in the name. 



A scientifick genelman, our Genius on the cruise, 

 ■Explained to us the hanimals, their habits, and their use ; 

 1 don't tumble to it much ; but. Kill, he spun a yarn 

 About the objeck of the cruise which I was glad to lam. 

 He said 'twas fur the good of man to r.iise him summat higher, 

 Since it was proved by some one that a monkey was his sire ; 

 I don't see how it foUers — but he sed from wat lie found 

 There was fields of blazing sea weed below upon the ground ; 

 And every little blessed thing we drugc out of the sea 

 Was for the good of all mankind, including u and me. 

 He likewise said, and bid us all partikilarly remark, 

 That at the bottom also 'twas most exceedin' dark. 

 Cause from twenty million fathoms once we got a curus prize 

 (He didn't want 'em in the dark) a iisl-. with many eyes. 

 He told us that we'd all be dooks when this 'ere cruise is done ; 

 I think he was mistaken, or he meant he would be one. 



Thare goes the pipe, my hearty ; so I'll no more at present 



write 

 But ax you to believe yours most faithful 



Jack Skylight 



THE COMMON FROG* 

 X. 



The Nervous System of the Frog. 

 'TPHE nervous sj-stem consists of the brain, spinal mar- 

 -*- row, and nerves. 



The whole consists of a soft, white substance, uhimately 

 composed of minute threads, termed nerve-fibres, and 

 minute round bodies called "ganglionic corpuscles." 



The brain is contained in the cavity of the skull, and 

 consists of a rounded mass made up of corpuscles and 

 fibres, and itself contains a cavity which is a remnant of 

 the original canal formed by the upgrowth and overclosure 

 of the walls of the primitive groove of the embryo. 



The spinal marrow (as has been said earlier), traverses 

 the canaKormed by the successive neural arches of the ver- 

 tebra2 being directly continuous with the brain which it, as 

 it were, continues on down the back. Like the brain, it is 

 largely composed of corpuscles, as well as fibres, and 

 itself contains a longitudinal cavity (continuous with that 

 in the brain), which is also the ultimate condition of the 

 canal formed from the primitive embryonic groo\-e. 



The ner\c5 generally (which arc made up of fibres) pro- 

 ceed forth from the brain and spinal marrow, which there- 

 fore are called the central, or (from their position along the 

 dorsal axis of the body), the axial portion of the nervous 

 system. 



All the nerves which so proceed together constitute 

 what is called the peripheral, or (because going to the 

 limbs which are appendages of the trunk), the appendienlar 

 portion of the nervous system. 



From the brain proceed the nerves of special sense : 

 a pair, one on each side, going to the nostrils (i, the 

 olfactory nerves), another pair going to the eyes (2, the 

 optic nerves), and a third pair going to the ears within 

 the skull (3, the aiulitory neives). Other nerves go to the 

 tongue and palate, ministering to taste, and again others 

 to the little musc'es (orbital muscles), which move the 

 eyeball in various directions, and to different parts of the 

 face. 



The nerves which come forth from the spinal marrow 

 are called spinal nerves. They proceed out in pairs (one 

 on each side), and are distributed to the limbs and trunk. 



Each nerve consists of fibres, of the sorts proceeding 

 respectively from the ventral (in man anterior), and the 

 dorsal (in man posterior) aspects of the spinal mat row. 

 But these two kinds of fibres are distributed side by side 

 in the ramifications and distributions of each nerve. 



* Continued from p. 266, 



The fibres which come ultimately from the dorsal aspect 

 of the spinal marrow are those which carry inwards the 

 effect of a stimulus applied towards their ultimate termi- 

 nation, and are therefore called affeirnt, or sensory. 



The fibres which come ultimately from the ventral 

 aspect of the spinal marrow, are those which carry an 

 mfluence outwards, and produce a contraction in the 

 muscles, and arc therefore called efferent or motor. 



It is the nervous system of the Frog, rather than any 

 other set of its organs, which has especially excited 

 interest and attention. It is especially to the relations 

 inter se, of the parts of this system that inquiry has been 

 directed. The relations, that is, of its central or axial 

 portion (the brain and spinal column) to its peripheral or 

 appendicular portion (the nerves of the body and limbs) 



In the ever memorable year 17S9, Galvani accidentally 

 discovered in the separated legs of certain Frogs, pre- 

 pared for broth, those motions produced by irritation of 

 the exposed_ great nerve of the thigh, now so familiar 

 to most. This action was long called galvanism, after this 

 observer, not, however, that he was absolutely the first 



to notice a fact of which he was but a re-discoverer 



Swammerdam as long ago as 1658 having observed such 

 motions. 



They are generally considered as demonstrating the 

 purely "reflex action"ofthenervous system— theresponsive 

 action, that is, upon muscles, of nervous centres acted on 

 by external stimuli without the intervention of sensation. 



It is affirmed that not only will a decapitated frog en- 

 deavour to remove an irritating instrument by means of 

 its hind legs and feet ; but that if a caustic fluid be ap- 

 plied to a spot easily reached by one foot, the decapitated 

 frog will apply that foot to the spot. More than this, if 

 that foot be cut off it will move the stump as before, seek- 

 ing to reach the spot, and failing so to do, will then apply 

 the other foot to the irritated locality. 



These, and such experiments, are of course conclusive, 

 if the common assumption be conceded that the brain is 

 the indispensable nervous instrument of sensation. 



It may be, however, that the faculty of sensation may 

 be subserved by the spinal cord without the brain, and if 

 so, all these much vaunted experiments are valueless as 

 regards the proof of pure reflex action, not but that they 

 are of extreme interest, as showing what may be done in 

 lower animals without the intervention of any brain action 

 whatever. 



Mr. G. H. Lewes has long contended against the attri- 

 bution of sensation to the brain exclusively, and Dr. Bas- 

 tian has recently supported and enforced similar views. 



The latter remarks in his " Beginnings of Life," — "in- 

 stead of accepting the popular viev^', that the brain is the 

 organ of mind, I believe it would be nearer the truth to look 

 upon the whole nervous system as the organ of mind." 



Dr. Bastian here uses the word " mind," not as denoting 

 a rational intellect but as a generic term equivalent to 

 psychical activity. 



It may be remarked in passing that these views of 

 Messrs. Lewes and Bastian closely approximate, as far as 

 they go, to that most rational belief that the soul of every 

 creature is whole and entire in every atom of its bodily 

 structure so long as the latter preserves its integrity and 

 vital activity. 



The brain of the frog consists of the same essential parts 

 as does the brain of all the vertebrate animals, including 

 man. In the form and in the proportions of those parts, 

 however, it differs extremely from the higher animals (and 

 above all from man) and resembles the lower forms — the 

 brain of the frog (and of Batrachians generally) oil'ering a 

 much closer resemblance to that of a lizard than to that of 

 a mammal. 



The brain of man consists of the following fundamental 

 parts : 



I. A pair (one on each side) of small rounded bodie.<-, 

 each connected, by a long stalk, with the mass of the brain. 



