40 THE TONER LECTURES. 



tender cords in wliicli we may sometimes differentiate the 

 artery from tlie vein — an important point in prognosis. Week 

 by weelv, sometimes day by day, the i)rogress of the coagulum 

 may be traced upwards by the abolition of the pulsation and 

 by the upward march of the gangrene. If old cicatrices exist 

 they will be among the earliest parts to yield. Blebs may 

 form in the early stages, but most frequently they will dry up 

 and the parts will mummify, although, as already indicated, 

 moist gangrene may supervene if a large clot form higher up 

 or if the veins are extensively obliterated, thus involving great 

 masses of moist tissue, such as the thigh, in sudden ruin. 



Life may be rapidly destroyed, as in a case recorded by 

 Barker and Cheyne,^ in two and one half liours after gangrene 

 began in the nose; but more commonly da3's or weeks will 

 elapse during which nature as usual makes a powerful effort 

 to rid herself of the dead parts b}^ the establishment of a line 

 of demarcation. On the establishment of this, the pain often 

 ceases. 



If recovery follow, the circulation is carried on by collateral 

 branches, or in very rare cases the artery again becomes par- 

 tially pervious.^ This last result Humphrey has shown to be 

 not infrequent in veins, and Petres' has recently elucidated its 

 mechanism through the extension and coalescence of the vasa 

 vasorum. 



In the variety of gangrene without a thrombus, the symptoms 

 will vary somewhat. It is not so uniformly in the lower 

 extremity, and is much more frequently symmetrical. If small 

 in extent, pain is not apt to be a leading feature. The onset 

 is often earlier, and from the nature of the case its progress is 

 sharper and its limits much more quickly defined, so that 

 usuallj'', within a few days at least, the boundary of the gan- 



> Yol. i. p. 232. 2 Patry, Archiv. C^n.. lHfi3, i. 136. 



8 Ediab. Journ., Aug. 1875, p. 17.5, from Le Progrfes Med. 



