ttt PHYSICAL FORCES. CORRELATION OF. 



PHYSICIAN. 



t in modern science,* principle startling at first, but 

 when cloarly understood and firmly grasped, almost axiomatic. It 

 must be considered a necessary truth, and, a* uch, u a legitimate 

 b**u of deductive naaoaing. The correUtion of physical forces ii 

 universally recognised at a principle in science, and not only so, but 

 luu already been productive of many beautiful and useful results." 

 Kor Profe**or Le C<>nU>' application of the principle to the history of 

 organic nature, we must refer to the paper itself. ' Amer. Joum. of 

 Science,' Nor. 1859, reprinted in ' Phil. Mag. Fourth Series,' vol. xix., 

 p. 1SS. 



Again, in the introductory address delivered on the opening of St. 

 Thomas's Hospital Medical College, Southwark, London, on the 1st of 

 the present month (October, 1*60) by Mr. K. D. Grainger, F.R.S., 

 which has the emphasis of being also a valedictory address on his 

 retirement from the chair of physiology in that school, we find the 

 following pisssflos. which are here cited, not merely for the purpose of 

 "^rfi!"; for Mr. Grove what of right belongs to him, but because we 

 have in them the sentiments of an eminent physiologist on the cor- 

 relation of the vital and physical forces. " In the case of the forces 

 implicated respectively in inorganic and organised bodies, it may in 

 the present state of knowledge be very difficult to demonstrate their 

 ultimate identity. Nor need this be a matter of surprise when we 

 recollect how very recently the intimate relations of the several 

 physical forces themselves have been discovered by such researches as 

 those of Oersted, Faraday, and Graham. Chemical force, electricity, 

 magnetism, caloric, and light, act and react on each other in the mode 

 signified by the term correlation, and are probably, as many profound 

 philosophers suppose, only different manifestations of one universal all- 

 prevading force.' Proceeding next to the organic forces, the experi- 

 ments of Matteuci on the nervous and muscular forces are noticed, 

 together with Dr. Todd's proof that the latter is not itself electricity, 

 the evidence of which is stated to be afforded by " phenomena the 

 very counterpart of what Professor Miiller pointed out years ago, in 

 regard to the nervous and electric forces." " Now, although," Mr. 

 Grainger continues, " this may seem to indicate an ultimate and essen- 

 tial ditference between the electric and muscular currents, it presents 

 the very same condition of things as that expressed by the term 

 ' correlation of forces.'" Farther on he alludes to the maxim, that there 

 is no creation of force, observing that " no force is ever manifested 

 without an equivalent change of matter, which change, according to 

 the wide generalisation of one of our former colleagues, my friend. Dr. 

 Lesson, is in every form light, electricity, magnetism, gravitation, 

 Ac. ultimately resolvable into motion." ' Lancet,' 1860, vol. ii. 

 p. 852, 353. 



Whether Dr. Leeson's generalisation was enunciated prior to Mr. 

 Grove's we are not aware ; but it is simply one elementary correlation 

 of the latter. The reader will have observed that while the doctrine, 

 as well as the designation, of the correlation of forces is fully adopted, 

 Mr. Grove's name is not mentioned ; uor does it occur anywhere in 

 Mr. Grainger's address. 



We have endeavoured in this article to do justice to Mr. Grove, and 

 . to the subject to which he has devoted so much attention and thought. 

 The progress of science, in its approach to the abstract truth, consists 

 partly in the ascent to higher and higher generalisations successively, 

 J and partly in the limitation of generalisations previously attained, or, in 

 I other words, the verification of hypotheses. Fully believing the doctrine 

 ' of the correlation of physical force*, we stated several years since our 

 ! opinion that that doctrine is the expression of the deeper or higher 

 truth, that they are all, not excluding mechanical force, effects, or 

 affections, of the ether, the ether of Hooke, Young, and Fresnel, and 

 generally of the mathematicians and physicists who have advocated the 

 undulatory theory of light and of heat. In the ' Philosophical Maga- 

 zine ' for January, 1859, Professor Challis of Cambridge, thus intro- 

 duces his theory of the principle : " It appears to be established by 

 modern experimental researches, that the different physical forces .ire 

 mutually reUted by some common condition, or bond of connexion ; 

 but what the precise nature of the connexion is. perhaps experiment 

 alone U incapable of determining. This generalisation will become 

 matter of exact knowledge only when it is brought within the domain 

 of mathematics. The great desideratum of the existing state of natural 

 philosophy is a math natiral theory of pkyrical forctt. After the 

 explanations that hare been given of a great variety of the phenomena 

 of light, which is one of those forces, by the hypothesis of a highly 

 elastic medium pervading space, it U not a little surprising that an 

 explanation of the ' correlation ' of the several forces should not have 

 been sought for in the existence of this medium, which would seem to 

 be a vast reservoir of force sufficient to account for all observed 

 dynamical effects." Professor Challis has pursued this subject in a 

 series of elaborate analytical investigations, also published in the 

 ' Philosophical Magazine ' for 1859 and 1860. "The principal hypo- 

 thesis of the theory U, that the physical forces are all consequences of 

 the motions and praxuns of a uniform and highly clastic medium 

 pervading space. The variations of the pressures of the medium are 

 supposed to be proportional to variations of its dennity ; and this sup- 

 position forms the basis of a mathematical investigation of the relations 

 between the motions and the pressures. Further, it U assumed that 

 the medium acts immediately by prcMiire on the ultimate atoms of 

 bodies, which are all supposed to be spheres of invariable magnitudes 



and of the same intrinsic inertia. According to those hypotheses, the 

 different phenomena and properties of bodies de|x-ml only on the mag- 

 of their atoms, the proportion! in which they 



are composed of 



atoms of difemt magnitudes, and on the arramjrmrnti of the atoms." 

 As the explanation of the sensible properties of matter must be pre- 

 ceded by a mathematical investigation of the laws of the dynamic 

 action of the assumed etherial medium, Professor Challis has 

 already entered on such an investigation relatively to light, heat, 

 the force of gravity, the forces of molecular aggregation, and the- 

 force of electricity; and is still proceeding with the explanation of his 

 theory. 



We will conclude this article by the suggestion that progress in 

 natural philosophy, in both the directions indicated above, would 

 probably be effected by the experimental and mathematical investiga- 

 tion of the following theorem : 



Taking ipaee to be the extension of material substance, the resultant 

 of its dimensions, and mere consequence of its existence ; and . 

 to be the substitution of one portion of matter for another, identical 

 with the succession of phenomena, our perception of which is time: 

 heat and light are correlates of each other, being also, as wo receive 

 them from the sun, and as existing in their terrestrial form, affec- 

 tions of an ether pervading space and ordinary ponderable matter; 

 but acting as the initiating forces in respect of electricity, mag- 

 netism, and chemical affinity, which are correlates of each other of 

 a different order, and derivative affections of the ether (perhaps, also, 

 derivatively from the ether, of the matter exhibiting their phenomena), 

 the apparent production of heat and light by them being in reality the 

 riWu/ioa only of those initiating forces : all these forces have the power 

 of substituting one portion of matter for another, or of causing motion ; 

 the apparent agency of time and motion being merely the continu- 

 ance and consequent accumulation of action. 



PHYSICIAN (4 Quo-mis), a word derived from Qvau, nature, which 

 meant originally what we should now call a natural philosopher, or one 

 of those persons who have for their object the investigation of nature 

 and its laws, in opposition to oi riffucol, or those who examine particu- 

 larly into the moral nature of men. [PHILOSOPHY.] In English how- 

 ever the word physiaan is used only to designate the professors of the 

 healing art, called in Greek iarpoi, and in Latin medici ; while in most 

 (if not all) other European lanaguages the derivatives of the Greek 

 word are still employed in their original meaning, and the idea of 

 healin'i is expressed either by some native word or by one derived 

 from the Latin.* The origin and progress of physic, together with an 

 account of the different medical sects, has been given already under 

 MEDICINE ; in the present article it is proposed to mention some of 

 the most curious and interesting facts respecting the rank, education, 

 4c., of the physicians of antiquity, and afterwards to state the legal 

 qualifications for practising this branch of the medical profession in 

 our own country. 



In Greece and Asia Minor the profession of medicine seems to have 

 been held in high esteem, for, not to mention the apotheosis of ^Escu- 

 lapius, who was considered as the father of it, there was a law at 

 Athens that no female or store should practise it (Hyginus, ' Fab.,' cap. 

 274) ; jElian mentions one of the laws of Zaleucus among the Epize- 

 phyrian Locrians, by which it was ordered that if any one during his 

 illness should drink, wine contrary to the orders of his physician, even 

 if he should recover, he should be put to death for bis disobedience 

 (' Var. Hist.' lib. ii., cap. 37) ; and there are extant several medals 

 struck by the people of Smyrna in honour of different persons belong- 

 ing to the medical profession. (Mead's ' Dissertatio de Nummis qui- 

 husdam & Smyrnxis in Medicorum Honorem percussis,' 4 to., Loud. 17-1) 

 If the Decree of the Athenians (published among the letters of Hippo. 

 crates) be genuine, and if Soranus (' in Vita Hippocr.') can be depended 

 on, the same honours were conferred upon that physician as had before 

 been given to Hercules ; he was voted a golden crown, publicly initiated 

 into the Eleusinian mysteries, and maintained in the Prytaneum at the 

 state's expense. (See also Pliny, ' Hist. Nat.,' lib. vii., cap. 37.) Some 

 idea of the income of a physician in those times may be formed from 

 the fact mentioned by Herodotus (lib. iii., cap. 131 >, that the ^Gginetans 

 (about the year B.o. 532, 01. 62, 1) paid Democedes from the public 

 treasury one talent per annum for his services, that is (if we reckon, 

 with Hussey, ' Antient Weights and Money, Ac.' the ,ginetan drachma 

 to bo worth 1. IJd.), not quite three hundred and forty-four pounds; 

 he afterwards received from the Athenians one hundred minic, that is 

 (reckoning, with Hussey, the Attic drachma to be worth 9 jrf.), rather 

 more than four hundred and six pounds ; and he was finally attracted 

 to Samoa by being offered by Polycrates a salary of two talents, that is 

 (if the Attic standard be meant) four hundred and eighty-seven pounds 

 ten shillings. It should however be added that Valckenaer doubts the 

 accuracy of this statement of Herodotus with respect to the vKginetans 

 and Athenians (and apparently with reason), on the ground that the 

 latter people, at the time of their greatest wealth, only allowed their 

 ambassadors two drachma! (or It. lid) per day, that is, somewhat less 

 than thirty pounds per annum. (Anstoph., ' Acharn.,' v. 66.) It 

 seems to have been not uncommon in those times (as afterwards in the 



Somewhat nnalopoui to thin U the u- of the Arabic word hakim (from 

 kaltama, ' novlt ' ' sapiens full ') which properly moan* a true or learned man in 

 (aeral, but U very frequently used in a restricted senie to ilgnlfy a phytician. 



