44 APPENDIX, 



moved a portion of scirrhous pleura, thus allowing the pericardium to be expo&ecL- 

 The patient was perfectly insensible of any impression, when M. Iticherand touched 

 this organ, although the pericardium, the part through which it was handled, is evi- 

 dently the must sensible part of it during disease : in a'state of disease its organic sen- 

 sibly becomes indistinctly and obscurely developed. 



TI. Of the Arteries. The arteries throughout the body are smTOunded by the gan- 

 glial nerves. These nerves form a reticulum around them, from which reticulum very 

 minute fibrillse are given off and dip into their fibrous or muscular tunic. 



This particular disposition of the ganglial nerves on the arteries ought to be kept in 

 recollection when we inquire into the functions of the latter. How far it tends, not 

 only to the discharge of the more manifest actions which the arterial system performs, 

 bvit also to those insensible changes which the blood undergoes in health and in dis- 

 ease, and to the assimilation of the chyle and other absorbed materials conveyed into 

 this fluid, we have ventured to state at another place. We shall here merely take no- 

 tice of an opinion relative to the operations of this class of vessels in the circulation of 

 the blood, lately contended for by M. Magendie. This physiologist has inferred from 

 his researches on the circulation, 



*< 1. That neither the larger nor the smaller arteries present any trace of irritability. 



2. That they are dilated during the heart's systole. 



"3. That they are capable of contracting themselves with sufficient force on the 

 blood they contain, so as to propel it into the veins. 



" 4. That the blood in the arteries is not alternately at rest and in motion ; but that 

 it is, on the contrary, in a continued succedaneous (by little jets) motion in the trunks 

 and ramifications and uniform in the smallest ramifications and divisions. 



5. That the contraction of the left ventricle of the heart, and the elasticity of the 

 larger and smaller arteries, furnishes a satisfactory mechanical reason for these pheno- 

 mena, 



" 6. That the contraction of the heart and arteries has a considerable influence on the 

 coxirse of the blood through the veins." 



We cannot concur in these conclusions, especially in the sweeping inference which 

 forms M. Magendie's fifth proposition : and we might, were it consistent with our limits, 

 point out various fallacies in his experiments, to some of which, indeed, all experiments 

 on living subjects are more or less liable, viz. the unnatural position of the animal dur- 

 ing their performance, and more particularly as respects the operations of the part im- 

 mediately its subject. If M. Magendie limits the process to the mechanical means in- 

 dicated above, we would ask, how he accounts for the influence of mental emotions in 

 determining the action of the vessels in particular parts of the body ? How the diversi- 

 fied influences of numerous external agents on the circulation can be explained ? 

 Wherefore so very opposite effects are produced upon the arteries, when one extremity 

 is placed in a pail of ice, and another in a pail of warm water ? How can he reconcile 

 his conclusions with the very satisfactory experiments performed by Sir Everard Home, 

 Dr. Hastings, and others ? and how he can account for the determinations of blood to 

 particular parts, whilst a diminishing quantity is sent to other situations ? if he discard 

 lite predominating or vital power which the vessels themselves, and especially their 

 smaller ramifications possess in virtue of the particular structure already noticed. We 

 readily grant that the larger branches of arteries evince little or lio contractile action, 

 particularly in their natural state ; but we contend that it increases as we advance to- 

 \yards the extreme capillaries, the action of which derives the blood to them in larger 

 proportion, and thus increases both the mechanical and vital properties of the larger 

 branches supplying them. 



We allow that the properties for which M. Magendie contends have an actual place 

 in the process of arterial circulation ; but they are not the only ones ; they are insufficient 

 of themselves to accomplish the purposes which he assigns to them ; and, moreover, 

 they are secondary to, and controlled by, a superior influence. 



From these observations it may be perceived that the arteries act in the process of 

 the circulation, not by means of a contractile action similar to what is performed by the 

 heart ; nor yet by means of elasticity only ,- but by an organic or vital operation, which is 

 nearly imperceptible in the larger arterial branches, but which increases as we advance 

 to the extreme capillaries ; whilst, on the contrary, the elastic or mechanical properties 

 augment as we proceed in the opposite direction. 



