30G SEROUS MEMBKAXES. 



1 can only allude by the way to the great variety of the irritants 

 •which determine the course of the inflammatory process in accordance 

 with their respective intensity and quahty. Most of them act chemi- 

 cally ; the simplest case is when a foreign liquid is extravasated at 

 some point into the serous cavity (perforation of the stomach, intestine or 

 gall-bladder ; bursting of an abscess or a gangrenous nodule ; entrance 

 of morbid secretions from the uterus and Fallopian tubes into the peri- 

 toneal sac, &c.). The etiology of peritonitis, pleurisy and pericarditis 

 in zymotic diseases and rheumatism is more obscure. Here we must 

 recollect that the serous cavities are to be viewed simply as interstices in 

 the connective tissue. Hence the fluid contained in the cavities partici- 

 pates in whatever changes the composition of the liquor sanguinis may 

 undergo. Since the discovery by Von BecMinghausen of the absorbent 

 stigmata of lymphatic vessels on the serous lining of the diaphragm, we 

 may go so far as to assert that the fluid contained in a serous cavity is 

 subject to a certain change or renewal. Any irritant material which 

 may exist in the liquor sanguinis is thus all the more likely to find its 

 way into the serous cavity. And here, just as in the joints and endo- 

 cardium, a second factor comes in to increase the irritation (may we say, 

 zymotic?) set up by the materies morhi ; I refer to the gliding of the 

 opposed surfaces of the serous sac upon one another. In consequence 

 of this, the one surface actually rubs the infecting matter into the other, 

 and I do not scruple to regard this as a concurrent element in the pro- 

 duction of the inflammation. 



The displacement which the viscera physiologically undergo, and 

 the consequent shifting of the opposed surfaces of the serous sac upon 

 one another, contribute in great measure (as will presently be shown) to 

 the extension of a local inflammatory irritation over the whole of the 

 serous surface. 



Owing to their greater simplicity, and the greater ease with which 

 they can be followed, we will first direct our attention to the movements 

 of the lungs in respiration, and the gliding of the pulmonary upon the 

 parietal pleura. During the act of inspiration, the lung expands in all 

 its dimensions ; during expiration it undergoes a proportionate con- 

 traction. The size and shape of the thoracic cavity adapt themselves at 

 each successive moment to those of the lungs, the contact between them 

 never being broken. How do the pleurse behave in the meantime ? 

 While the pulmonary pleura accompanies the lung in its expansion and 

 contraction, the parietal pleura, attached to the thoracic wall, undergoes 

 the diminution required during the expiratory act, by becoming folded 

 upon itself at its edges. So that it is only at the close of a deep inspira- 

 tion that the two pleurae are everywhere in contact (fig. 97). At the 

 beginning of expiration, the edge of the lung (r), and with it the extreme 



researches conducted in the Pathological Institute of Bonn under my 

 supervision by Br. Milnch of Saratof. All the figures marked Mch. are 

 borrowed from him. 



