'262 THE PLEURA. 



absorbents is diniinishcd, the fluid rapidly and greatly accumulates. Thus 

 we have hj'drothorax or dropsy of the chest, as one of the consequences of 

 inflammation of the chest ; and the same disturbed balance of action will 

 produce similar eflPusion in other cavities. 



The adaptation of membrane generally is nowhere more strikingly dis- 

 played than in the serous membranes, and particularly in that under con- 

 sideration. How different the bulk of the lungs before the act of inspira- 

 tion has commenced, and after it has been completed, and especially in the 

 laborious respiration of disease or rapid exertion ! In either state of the 

 lungs the pleui-a is perfectly fitted to that which it envelopes. 



The pleura, like other serous membranes, is possessed of very little 

 sensibility. Few nerves from the sensitive column of the spinal cord 

 reach it. Acute feeling would render these membranes generally, and 

 this membrane in particular, unfit for the function they have to discharge. 

 It has too much motion, even during sleep ; and far too forcible friction 

 with the parietes of the thorax in moi-bid or hurried respiration, to render 

 it convenient or useful for it to possess much sensation. Some of those 

 anatomists, whose experiments on the living animal do no credit to their 

 humanity, have given most singular proof of the insensibility, not only 

 of these serous membranes, but of the organs which they invest. Bichat 

 frequently examined the spleen of dogs. He detached it from some of its 

 fidhesions, and left it protruding from the wound in the abdomen, in order 

 ' to study the phenomena ; ' and he saw ' them tearing off that organ, and 

 eating it, and thus feeding upon their own substance.' In some experi- 

 ments, in which part of their intestines "were left out, he observed them, 

 as soon as they had the opportunity, tear to pieces their own viscera with- 

 out any visible pain. 



Although it may be advantageous that these important organs shall be 

 thus devoid of sensibility when in health, in order that we may be 

 unconscious of theii' action and motion, and that they may be rendered 

 perfectly independent of the will, yet it is equally needful that, by the 

 feeling of pain, we should be wai'ued of the existence of any dangerous 

 disease : and thence it happens that this membrane, and also the organ 

 which it invests, acquire under inflammation the highest degree of sensi- 

 bility. The countenance of the horse labouring under pleurisy or pneu- 

 monia will sufiiciently indicate a state of suffering ; and the spasmed bend 

 of his neck, and his long and anxious and intense gaze upon his side, tell 

 us that that suffering is extreme. 



Nature, however, is wise and benevolent even here. It is not of every 

 morbid affection, or morbid change, that the animal is conscious. If a 

 mucous membrane is diseased, he is rendered painfully aware of that, for 

 neither respiration nor digestion could be perfectly carried on while there 

 "was any considerable lesion of it ; but, on the other hand, we find tubercles 

 in the parenchyma of the lungs, or induration or hepatisation of their 

 substance, or extensive adhesions, of which there were few or no indica- 

 tions during life. 



The pleura adheres intimately to the ribs and to the substance of the 

 lungs, yet it is a very singular connection. It is not a continuance of the 

 same organisation ; it is not an interchange of vessels. The organ and its 

 membrane, although so closely connected for a particular purpose, yet in 

 very many cases, and where it would least of all be suspected, have little 

 or no sympathy with each other. Inflammation of the lungs will some- 

 times exist, and "will run on to disorganisation, while the pleura will be 

 very little affected : and, much oftener, the pleura will be the seat of 

 inflammation and will be attended by increased exhalation to such an 

 extent as to suffocate the animal, and yet the lungs mil exhibit little other 



