326 SEEOUS MEMBRANES. 



effaced, the lung undergoes a diminution in size greater tlian 

 could be produced bj its own elasticity ; it contains no air, and 

 hangs in the pm^ulent fluid as a narrow strip of leathery tissue, 

 hardly as broad as the hand. Finally, the pus seeks a mode of 

 exit, just like an abscess. In the case of an empyema the spot 

 chosen for perforation is usually one of the lower intercostal 

 spaces ; here how^eyer the art of the physician usually interferes, 

 disturbs the natural but somewhat tardy course of eyents, and 

 determines the point of exit y/ith a trocar. 



§ 278. As regards the further progress, i.e. the gradual 

 repair of the morbid state, we may argue from our experience of 

 union by the second intention, with this limitation, howeyer, 

 that in the present case cicatrisation occurs on a scale pro- 

 portionate to the colossal size of the ulcerating surface. We 

 find the usual series of embryonic tissue, spindle-cell tissue, and 

 rigid, short-fibred cicatricial tissue — each member of the series 

 being deyeloped fi'om its predecessor, as is fully set forth in 

 ^ dS et seqq. Tlie cicatricial tissue presents itself in no small 

 proportions ; it forms a white and lustrous, fibroid stratum, from 

 half a line to tln-ee lines in thickness, ydiicli clothes the serous 

 cayity, and is stretched oyer the adjacent organs. This huge 

 cicatrix contracts like any other scar, and causes mechanical 

 effects of an imposing order. It is an admirable illustration of 

 tlie gigantic results which nature is able to produce by the addi- 

 tiye repetition of fractional moments of the same order. And 

 yet the resistance to be oyercome during the healing of an 

 empyema which has opened externally, is nothing less than that 

 of the yaidted arches of the thoracic skeleton which haye to be 

 dragged inwards, in a direction, that is, which the whole aim of 

 their being is to resist. There is an erroneous impression, 

 afloat, that the cicatrising process is able to help the expansion 

 of Jthe collapsed lung. But experience teaches us, as might 

 have been expected a priori^ that it is the fibroid tissue which 

 serves permanently to compress the lung. Sooner than allow of 

 any such expansion, the remaining thoracic viscera, sc. the 

 heart, are dragged over to occupy the space which was formerly 

 filled by the collapsed lung. Ko Torricellian vacuum is 

 produced. The stress is borne by the neighbouring organs, 

 which are dragged out of their places. The fibroid sac into 



