(1840) was, as stated by the preface, a second edition of these essays.*

IV. So much as to dates; next as to the method of inquiry. Dr. Carpenter is of opinion that the desired knowledge is to be attained by a study of the comparative anatomy of the nervous system, more especially of vertebrates, and hints that I did not appreciate the truth of the principles upon which his sensori-motor system is founded, because I was deficient in that knowledge. The obvious objection to this method is, that the inquirer never car know, as facts of observation, what are the states of consciousness of lower animals when inquiring into its relations to their mechanism. True it is, that for the sake of comparison with the mechanism and energies of man that knowledge is needed; but it is an error of inference on the part of Dr. Carpenter that I had not the knowledge. This error is, however, of little importance. It is, perhaps, sufficient to say that, like Dr. Carpenter himself, I studied Comparative Anatomy at University College under "the English Cuvier "-Robt. E. Grant-and was a diligent reader of Dr. Carpenter's "Principles of Human and Comparative Physiology." But in the course of my inquiries (after 1845) I came also upon the "Zoologie Philosophique," of Lamarck-an important forerunner of Darwin, who showed not only the mechanism of living things, but the processes by which that mechanism is both constituted and moved. It was also by the aid of such generalisations as those of Wolff, Goethe, and von Baer, that I was led to use more firmly than I otherwise should have done the hypothesis of evolution, to which I added that of reversion as the law of both mental and general pathology. In the essay published in July, 1839 (but which was in the hands of the editor of the "Edinburgh Medical and Surgical Journal" during the previous autumn), will be found the outline of that method laid down, and the law of evolution taken as the guide to inquiry as follows:

"20. If we would obtain a large and definite knowledge of the action of force [as motion] upon matter and intelligence, in exciting the phenomena of life and thought as displayed in man, we must

* By T. Laycock, House-Surgeon to the York County Hospital: A Selection of Cases presenting Aggravated and Irregular Forms of Hysteria, with Analysis of their Phenomena. Edinburgh Medical and Surgical Journal, Jan., 1838. Hysterical Ischuria, April, 1838. Hysterical Hæmorrhages and Nervous Affections and part of Analysis, July, 1838. Analysis continued, October, 1838. Analytical Essay, July, 1839.

examine the law of its action [i.e., of force as motion] as exhibited both in every living organism and in the molecular changes of inorganic matter. A thousand circumstances assure us that between these last and the highest efforts of the human intellect, there is a continuous chain of phenomena, although we have been unable to follow it link by link. These links are so continuous between certain vegetables and animals of the lowest class that naturalists have been unable to decide whether the organism should be placed in the animal or the vegetable kingdom."-(p. 9, op. cit.)

Here, then, is a statement that we have molecular physics and energies as vital chemistry to deal with evolutionally, in our investigation into life and thought and will, and that the law of continuous evolution is the guiding principle. This is followed by a short exposition of the evolutional mechanism, i.e., the evolutional anatomy of the nervous system.

From these facts it is clear, I trust, that there has been a fundamental difference ab initio between Dr. Carpenter and me as to method; for although he dealt restrictedly with the mechanism evolutionally, in so far as the nervous system is concerned, through its comparative anatomy, on the other hand he at that time left wholly out of consideration the evolutional anatomy of the hemispherical ganglia, and therewith the evolution of the vital energies or forces into mental activity. How little his method served him, and many others who followed this method, in elucidating brain function, is shown by what Dr. Carpenter had to say in regard to its results at this same date :

"The complexity of the operations of the mind, and the impossibility of deriving from the study of the lower animals any assistance which can be relied upon in their analogies, have hitherto been a complete bar to the successful investigation of them as portions of the nervous system. It is, as yet, quite uncertain how far mental acts are dependent on or connected with any changes in its condition." (Principles of General and Comparative Physiology. By W. B. Carpenter, Lond., 1838, p. 454.)

In the last paragraph Dr. Carpenter must only be understood as witnessing to his own convictions; the school of Gall and Spurzheim was then in full activity with a principle just the contrary. His was the doubt expressed then, as now, by "the old school of metaphysics," so that it is a matter of course that Dr. Carpenter should use the phrases and terms of that school, and this as much as ever in his latest work," Mental Physiology."

The method I followed in working out this unsolved problem was, in fact, to examine the analogies which Dr. Carpenter stated in 1839, in the extract just given, to be a complete bar to the exact study of cerebro-mental phenomena. But this I did by investigating sequences and coincidences, as well as differences and resemblances. In doing this I took the sequences and coincidences included under "spinal reflex function" as a starting point, and endeavoured to show that the actions or muscular movements under investigation exactly resemble, as to the condition under which they occur (or, in popular phrase their causes), the class of "reflex acts" and actions, whether they are named sensational, ideational, volitional, intellectual, instinctive, or involuntary; and are due to conditions or functions of brain or of nerve-centres, which conditions coincide with other conditions of brain upon which the states of consciousness named sensation, ideation, volition, will, or instinct depend.

It is, therefore, as to "the order of nature" in causation that Dr. Carpenter misunderstood me. I held that consciousness per se is not a cause, as taught by the "old metaphysics," but a coincidence-although as to evolutional life an essential coincidence; and, as such, the manifestation of an "immanent" energy, the cause of both life and conscious

ness.

It was as to this principle and its applications to certain departments of Mental Science and the practice of medicine that I made the reclamation alluded to. When with this view of causation I formally extended the doctrine of spinal reflex function to the brain, I certainly took care to state it as explicitly as language allowed. After premising a summary of spinal reflex phenomena in their relations to coincident sensations, which were then admitted (sensation denoting a state of consciousness of some kind-no matter how defined), I pointed out that all other states of consciousness, including ideation and volition, are not causes but coincidences of the acts, and themselves due to cerebral conditions or functions excited reflexly.* The actions occur, to use the words of Prochaska, "Mens conscia vel inscia." On the other hand Dr. Carpenter, noting a constant connection of states of consciousness named sensations with certain combined muscular movements, concluded that the sensation is an antecedent and not a coincident of the acts in question. In this way he

considered these states of consciousness to be causes.

"Brit. and For. Med. Rev.," vol. xix. (Jan., 1845), p. 299, 300.

Now this is precisely what was then the teaching of Alison and John Reid, as well as of Dr. Carpenter, and had been for a long period before that date of Whytt and others. It was, in fact, a part of the universally current opinion that consciousness in every form is the cause of certain movements. My object was to show that herein the coincident was put for the antecedent. It follows, therefore, that in the "Quarterly Review" for October, 1871, Dr. Carpenter states precisely the contrary to my view when he affirms that I showed involuntary muscular movements take place in respondence to sensations, and not merely to sensations, but to ideas." This is probably one of the propositions which Dr. Ireland thinks to be a child of the old metaphysics, and which it certainly is.

V.-But another source of error is to be found in Dr. Carpenter's ambiguous use of the phrases reflex action and reflex function in relation to the word sensation. As used by Hall, and by all physiologists since his time, reflex function wholly excluding sensation as a cause. The phrase was expressly adopted to set forth the doctrine that the class of actions termed reflex are wholly independent of sensation, whether it be considered a cause, or a condition, or a coincidence. When, therefore, Dr. Carpenter says that his doctrine of the reflex action (meaning function) of his sensori-motor system had been long previously taught by him, he is again in error, inasmuch as he confounds the conscious state named sensation with reflex function as a cause. This is clearly shown by his own words in the subjoined extract from a letter he wrote to Forbes in November, 1844, after reading my Essay in proof, which Forbes sent to him. The italics in the letter are in the original, thus giving the most conclusive proof of the ambiguity I have described.*

"I am much obliged by the sight of Laycock's paper, which is very much what I expected it to be. The class of actions to which he refers I had distinguished in my first paper on the subject. By my subsequent investigations I had been led to refer them to the ganglia of special sense, which stand in the same relation to the nerves of special sense as the segments of the true spinal cord to its afferent

I may properly remark here, as to this correspondence, that Forbes did not send the letters to me as being " private and confidential," but in his public capacity as Editor of the "Brit. and For. Med. Review," in which my essay was to appear, and with the request that I should point out in what particulars my views differed from those of Dr. Carpenter, with a view to publication with the Essay. I wrote an addendum in compliance with this request, which now lies before me, but Forbes did not publish it.

nerves, and which have also a distinct connection with the motor tract of the med. oblong. I did not apply the term reflex to them, because I considered it better to restrict that to the actions of the spinal cord. But I pointed out the immediate dependence of the motion upon the sensation, which is, in effect, the same thing. Dr. L. refers this class of actions (first distinguished and defined in the paper I allude to) to the cerebral hemispheres, which seems to me to imply an utter ignorance of the Comparative Anatomy of the Nervous Centres. I do not care to enter into a controversy on the subject. Magna est veritas, &c.-Yours most sincerely, W. B. CARPENTER."

In a subsequent letter to Forbes, dated 27th Nov., 1844, Dr. Carpenter entered more fully into the subject, and affirmed the emotional character-that is, as due to emotion -of the convulsive paroxyms of hydrophobia, as follows:

"I should like to know where he [Dr. L.] had pointed out the emotional nature of hydrophobia before my Human Physiology,' where it is pointedly stated, and the illustrations given. . . . . I had a battle to fight with Marshall Hall, who connected the emotional system with the spinal, and my comparison of tetanus went to prove their distinctness.'

The controversy with Hall here referred to arose out of ambiguities precisely like those I have illustrated. Hall fixed the limits of his "true spinal system" at the tubercula quadrigemina inclusive; these and all the nerve-centres below, including those of the cord and bulb, are merely physical centres, with which consciousness has no causal relation whatever; all above are the seat of, and are acted on by, the “soul.” Dr. Carpenter, on the other hand, included the tubercula and certain centres of the bulb in his "sensori-motor system." These are not, according to him, the seat of the soul, but of sensation; and "guiding sensations" seated here are the causes of consensual or "sensori-motor" actions. Hall naturally objected to the theories of both the anatomy and the causation, and more especially because the consensual actions, which are the signs of the instinctive feelings and emotions, were also included by Dr. Carpenter in his" sensorimotor system."

Whatever truth there may be in any of the hypotheses, these facts are instructive illustrations (and they might be greatly multiplied) of the misleading influence on physiological research of ambiguous terms and phrases, and more especially of those of "the old metaphysics." That they are thus generally operative is certain. Ten years later