Jan. 7, 1875] 



NATURE 



185 



venous blood increases, the latter force becomes relatively 

 more powerful." The most energetic of these auxiliary 

 pneumatic forces is stated to be that of the chest, which 

 is followed in importance by the suction force of the 

 heart and by a " pleuro-cardiac pneumatic force," in which 

 the heart, contracting in a rigid chamber, draws blood 

 into it from the surrounding veins, on account of its 

 decrease in size during the systolic act. The elaborate 

 investigations of MM. Chauveau and Marey,* published 

 a little more than ten years ago, put us in a position to 

 state exactly, in inches of mercury, what are the values of 

 the pneumatic forces which Dr. Buchanan describes ; and as 

 these results are evidently not familiar to British physio- 

 logists, to those at Glasgow at least, it may be worth 

 while recapitulating them here. First, the sphygmograph 

 trace in health shows that, as Dr. Arnott maintained, 

 normal respiration has scarcely any appreciable effect on 

 the blood-pressure, because the horizontal line joining 

 corresponding points in the difterent pulse-beats is very 

 nearly, if not quite, straight. These authors also explain 

 how the antagonistic results of Ludwig and Vierordt — in 

 which the one states that the blood-pressure falls during 

 inspiration, and the other during expiration — can be 

 accounted for ; they finding that if the air-passages are 

 partially obstructed, as by shutting the mouth and closing 

 one nostril, the one result is produced ; whilst if these 

 same passages are freely opened, the opposite effect is 

 observed. The influence of respiration may therefore be 

 dismissed as comparatively insignificant. 



That of the heart is much more considerable. By 

 means of a beautifully constructed piece of apparatus 

 M. Marey has been able to demonstrate the existence 

 and amount of the negative or suction forces, as far as 

 they are found to exist in the different cavities of the 

 heart, during the different parts of each cardiac pulsation. 

 His results are recorded by the graphic method,f and 

 their agreement among themselves is evidence of their 

 accuracy. The work referred to contains a full descrip- 

 tion of the apparatus employed. The following are the 

 results : — In the right ventricle the blood-pressure docs 

 not ever go beyond zero, except at its basal portion, 

 where it is sometimes found that a minute suction force 

 develops immediately after the closure of the aortic valves, 

 and then only. In the left ventricle an appreciable suc- 

 tion force is observed at the same time as in the right ; it 

 is, however, not great. It is impossible, by any means 

 yet devised, to get at the left auricle, but the right auricle 

 is easily arrived at from the jugular vein. In it the blood- 

 pressure is nearly always negative or below zero, it being 

 otherwise only during its systole. A study of the auri- 

 cular cardiogrjjph trace shows that immediately after the 

 auricular systole, which is the same thing as saying at 

 the commencement of the contraction of the ventricles, 

 the pressure in the auricle descends rapidly below zero ; 

 that the descent is broken by a small wave, and that the 

 suction force commences to diminish gradually after the 

 closure of the aortic valve, becoming ;/// a very short time 

 before that organ again contracts. The explanation of 

 these changes is not difficult. The rapid fall in the auri- 

 cular pressure during the ventricular contraction was 

 many years ago fully explained in a pecuharly able 



* Marey, ** Circulation du Sang ; '* Paris, i86j, 

 t Loc. cit. pp. 95, 96. 



memoir by Mr. Bryan,* and the active dilatation of the 

 ventricles of the heart durigg diastole, which necessitates 

 a corresponding internal suction force, has been shown 

 by more than one physiologist to depend on the peculiari- 

 ties of the coronary circulation. 



By employing a specially adapted manometer M. Marey 

 was able to measure this suction force in the right auricle 

 of Eqiiiis eahallus, and found that it ranges, on the 

 average, between - 7 and - 15 millimetres of mercury, 

 the same method giving 120 millimetres as the average 

 pressure in the left ventricle during the systole. From 

 these figures the true relation borne by the contractile 

 force of the heart to its suction' power can be readily 

 estimated. 



The " pleuro-cardiac pneumonic force " described by 

 Dr. Buchanan is nothing more than that above referred 

 to as described by l\Ir. Bryan, the latter author having 

 previously demonstrated that on account of the heart — a 

 conical organ—contracting in a conical cavity, it must 

 necessarily advance towards the apex of that cone during 

 systole, and so leave the bise to be filled by the absorp • 

 tion of the blood from the distended veins. 



These remarks all tend to show that many of Dr. 

 Buchanan's investigations are in the right direction, but 

 that a further acquaintance with the literature of the sub- 

 ject would enable him to employ his considerable ingenuity 

 and enthusiasm in the elucidation of points still remain- 

 ing unexplained to students of the science of physiology. 

 This want of acquaintance with the works of others is, 

 we think, partly explained by some incidental remarks in 

 the book before us. The author says : " I have always 

 exercised all the branches of my profession. ... I can- 

 not but regard this custom as much superior to that 

 which our medical corporations are now enforcing, of 

 mak'ng every man from the beginning select for himself 

 a single branch of the profession ;" to which are added 

 other remarks derogatory to specialisation in study. 

 With these we cannot agree, and stilF think that "if you 

 wish to find a man of large views of physiological nature," 

 he is more likely to be a special student, with time at his 

 disposal, unoccupied by miscellaneous professional calls, 

 than one who, turning his attention to all things, has no 

 opportunity of concentrating it on any one, to the ad- 

 vancement of our knowledge of its details. 



OUR BOOK SHELF 



Elements of Animal P/iysiolo^y. Elementary Science 



Series. By J. Angell. (W.' Collins and Co., 1874.) 

 There is more than one way by which the relative im- 

 portance of scientific facts may be arrived at. An inves- 

 tigator, whilst prosecuting his independent researches, 

 will not be long in forming a fairly accurate standard, and 

 this he finds it easy to impart to others. Many engaged 

 in educational work find it impossible to afford the time 

 for independent observation or prolonged study, and yet 

 it is their ambition to give their pupils a fairly correct 

 estimate as to those of the innumerable facts surrounding 

 them on which they should lay stress in preparing for a 

 pass examination. The standard with them therefore 

 becomes nothing more nor less than the questions of 

 former years or of ether similar examinations ; the work 

 which answers the greatest number of these in the most 

 satisfactory manner being looked upon as the most 



* Lancet, Feb. 8, 1S34. 



