CIRCULATION. 



673 



ders probable the existence in them of some 

 power capable of propelling the blood inde- 

 pendently of the heart's action. 



6. That in the production of new vessels 

 which occurs in adhesion or granulation, the 

 new blood executes oscillatory motions in the 

 rudimentary vessels while in the act of form- 

 ing, before these parts of vessels are connected 

 with the previously existing branches through 

 which the heart propels the blood ; and this is 

 said also to occur in the formation of new ves- 

 sels in natural growth.* 



7. That in the formation of the vascular 

 area of the incubated egg the blood moves in 

 part through the veins and small vessels before 

 it is impelled by the action of the heart.f 



We would remark, regarding the oscillatory 

 and irregular motions described by Haller and 

 others as occurring in the small vessels of the 

 web after removal of the heart or ligature of 

 the aorta, that we believe some of these to be 

 caused by the elasticity of both the arteries 

 and veins, and others to be occasioned by the 

 gradual or tonic contractions which take place 

 in the arteries after death :J they occurred in all 

 Haller's observations, but in Spallanzani's only 

 when the apparatus of hooks constantly em- 

 ployed by Haller was applied ; and so far as we 

 have ourselves been able to observe them, we 

 have always found them influenced by very slight 

 changes. When one of the small vessels is 

 obstructed they cease altogether, which ought 

 not to be the case were they dependent upon 

 powers belonging to the capillaries or the blood 

 in them. Some varieties in the velocity and di- 

 rection of the blood in the smaller vessels we 

 have reason, from our own observations, to 

 attribute to the same causes, and we think it 

 consonant with such a supposition that heat or 

 other agents influencing the contraction of 

 arteries should influence these irregular mo- 

 tions. The oscillations of blood in parts of 

 vessels which are in the process of formation 

 in adhesions and granulations, or in natural 

 growth, we have not yet been able to observe so 

 clearly as to be certain that we were not de- 

 ceived ; but, even supposing them to have 

 been satisfactorily proved to occur, we should 

 be inclined to doubt the possibility of ascer- 

 taining with accuracy that these portions of 

 vessel are entirely shut off from all commu- 

 nication with other vessels, so as that no im- 

 pulse could be transmitted from the heart to 

 them. The necessity of some change in the 

 tissue of organs or of organizable lymph, in 

 which new vessels are about to be formed 

 before the propulsion of the blood into the 

 new loop of vessel seems sufficiently obvious, 



* BcelHnger, Journ. des Progres, &c. vol. ix. 

 Kaltenbrunner, loc. cit. Baumgartner, Beobacht. 

 iiber die Nerven und das Blut. Freiburg. 1830. 



t [Dr. Tanchose suggests as a cause for the mo- 

 tion of the blood in the capillaries, the ceaseless 

 removal of particles from the blood to supply ma- 

 terials to the various secretions, &c. a constant 

 tendency to a vacuum being thereby produced. 

 Acad. des Sciences, Seances d'Avril, 1833. ED.] 



t See Marshall Hall's Essay, p. 95 ; and also 

 Black's Inquiry, for judicious remarks upon these 

 oscillations. 



but it does not appear to be as yet satisfactorily 

 shewn that the motion of blood in the new 

 vessels is independent of a propulsion received 

 from the heart. Again we consider it as ascer- 

 tained that the heart of the chick acts just as 

 soon as any motion of fluids can be seen on 

 the vascular area of the yolk ; and though it 

 may be admitted that a certain change of place 

 in the particles of the yolk is necessary in the 

 new combinations which occur during the de- 

 velopment of the forming parts from its substance, 

 yet such a change or motion must be quite of 

 an insensible kind and not in any degree ana- 

 logous to the continued stream of circulating 

 blood through the vessels. 



The stagnation of venous blood in the capil- 

 laries of the lungs is certainly a most remark- 

 able and inexplicable phenomenon, but if from 

 analogy any weight is to be attached to obser- 

 vations made upon the frog, it may be stated 

 that the flow of blood through the lungs seems 

 as immediately dependent on the heart's action 

 as that through the system. The portal circu- 

 lation is not more remarkable in respect of its 

 isolation from the heart than the systemic cir- 

 culation of fishes, in which animals the capil- 

 laries of the gills intervene between the heart 

 and the systemic aorta ; and without any dis- 

 tinct contraction of that vessel, the circulation 

 of the blood in the systemic capillaries as 

 well as in the gills is very manifestly main- 

 tained chiefly, if not solely, by the action of 

 the heart. We do not feel inclined to attach 

 any importance to the alleged motions of the 

 globules of the blood out of the vessels, for 

 we have never been able to see any such in- 

 dicating different powers from those which 

 produce currents in inorganic fluids, and some 

 of the observations upon which the statement 

 is founded have been shewn to be erroneous. 



We think it unnecessary to do more than 

 merely to allude to some of the very many 

 attempts that have been made to account for 

 independent motion of blood in the capillaries, 

 or what have been termed the theories of the 

 capillary circulation. 



All that we know of capillary attraction mi- 

 litates against the possibility of its being the 

 means of causing a progressive motion of fluids, 

 sucli as that which occurs in plants and ani- 

 mals. Those who have attributed the motions 

 of fluids in the living body to endosmosis or a 

 principle of organic transudatiou, have failed 

 in pointing out in the bloodvessels the condi- 

 tions necessary for the occurrence of a motion 

 proceeding from- an action of this description. 

 The electrical theory is defective in this essen- 

 tial point, that no difference in the electrical 

 condition of the arterial and venous blood has 

 been shewn, and that the same cause to which 

 the motion of the capillaries of the systemic 

 arteries is ascribed ought to retard the passage 

 of blood in the pulmonary capillaries, the re- 

 lations of the two kinds of blood being 'there 

 reversed. The opinion that the motion of the 

 blood in the vessels is analogous to those cur- 

 rents of fluids which take place in contact with 

 the surfaces of various parts of animals, which 

 are almost always connected with ciliary mo- 



