OP THE MECHANISM OF THE RESPIRATORY ORGANS. 47 



of imbibition OP capillary attraction, which all animal textures evince in a greater or 

 less degree. It should, however, be recollected, that this property is a very subordinate 

 one to vitality, is entirely under its control, and takes place very imperfectly when this 

 influence is in full vigour, 



The second function of this class of vessels, is the' admixture of the absorbed mate- 

 rials, and the assimilation of them The former cr mechanical part of this function is 

 performed generally throughout the body, al hough it takes place to a greater extent 

 in some instances than in others, as in those viscera in which the blood circulates more 

 immediately after it has received the chyle and lymph from the lacteal absorbents and 

 thoracic duct. Hence it chiefly takes place in the heart itself, and in the liver and lungs. 

 The latter part of this function is essentially a vital one, and appears to us to result 

 from the vital influence derived from the nerves with which the blood-vessels are pro- 

 vided. Supposing this position to be correct, we should expect that the vessels in 

 which this process takes place would be most abundantly supplied with those nerves, 

 whence we consider the assimilating influence to proceed. Now this is actually the 

 case, the blood which is carried into the portal veins contains a larger proportion of ab- 

 sorbed and imperfectly assimilated materials than the blood in any other organ ; and this 

 particular order of veins, whose office it is to assimilate them, and to eliminate 

 the effoete elements from the circulating fluid, is provided with a much 

 greater number of ganglial nerves than any other part of the venous system ; and, in- 

 deed, even more than the arteries in some situations. This particular set of veins, 

 therefore, performs a double function, viz. of assimilation, and of secretion ; in the lat- 

 ter, however, it may participate with the hepatic artery ; for, as the hepatic vein re- 

 turns the blood of both the vena portee and the artery, the biliary secretion may, pro- 

 bably, not take place until the terminating capillaries of both have given rise to the 

 radicles of the vein. 



Assimilation goes on, in the next degree of activity, in the lungs, and more or less 

 partially in other organs of the body. 



Of the Mechanism of the Respiratory Organs. 

 Note U. 



I. Of the Structure of the Lungs. According to the observations of M. Magendie, the 

 cellules of the lungs do not appear to be arranged in a methodical manner, nor to have 

 membranous parietes. With respect to the non-existence of the latter, we think that 

 he was betrayed into error bv the method of investigation which he adopted.* These 

 cellules seemed to him to be formed solely by the minutest and last ramifications of the 

 pulmonary artery ; by the radicles of the veins of the same name, which are a 

 continuation of the former, and lastly, by the numerous anastamoses of all these ves- 

 sels. These cellules are separated into many distinct lobules, in each of which the 

 cellules communicate among themselves ; while between the lobules there is no com- 

 munication. 



" The number of cellules is in an inverse ratio to the age of the subject ; consequent- 

 ly the older the person, the larger is each cellula, or what comes to the same thing, 

 the fewer are the cellulx. 



*' It follows, therefore, that the lungs become specifically lighter as we advance in 

 fife ; and in support of the correctness of this inference Magendie states that he found, 

 by actual experiment, that in equal volumes, a portion of the lungs of a man at seventy 

 was fourteen times specifically lighter than that of a child a few days old." 



II. Of the Jlctiom of the Glottis M. Bourdon, (Recliei*che6 sur le mechanisms de la res- 

 wrafc'on, &c. Paris, 1820,) considers that the glottis performs the following functions^ 



in addition to those which are requisite to the formation of the voice. 



1. " That is the glottis which suspends respiration during considerable efforts, in op- 

 posing, by its closure, the escape of the air contained in the lungs. 





* He partially filled the lungs by insufflation after their removal from the subject, 

 and allowed them to dry. When quite dry he found this sort of preparation to be nearly 

 transparent, and readilv cnt into thin slices ^yith a knife- 



