12 NECROSIS OF TISSUES. 



It is only when the above mentioned jelly-like condition of 

 the decaying fibres is especially well marked that w^e may expect 

 to find the manner of their dissolution somewhat modified. It 

 was in a case of fairlv circumscribed (Tano-rene of half the foot, 

 due to frost-bite, that I first noticed that condition, and with it a 

 break-up of the fibres into Bowanan's discs ; since then I have 

 had an opportunity of confirming my original observation 



(fig. i,d). 



§ 16. Nothing is at present known about the necrosis of 

 NERVE- CELLS, and very little about that of the peripheric nerve- 

 fibres. We know that the thicker nerve-trunks maintain them- 

 selves in the interior of gangrenous parts for a relatively long 

 time, while, on the other hand, their finer branches undergo very 

 rapid decomposition. It is probable, from the analogy of rigor 

 mortis, that a coagulation of the medullary substance precedes 

 any farther changes. Accordingly the fluid matter between the 

 axis cylinder and the neurilemma, which is normally quite homo- 

 geneous, runs together to form globules of various sizes, which 

 are separated by a clear fluid. The dark and wavy outlines of 

 these drops impart a highly irregular aspect to the entire fibre 

 (fig. 8, a), which has not inaptly been compared to the spiral 

 curls of smoke from a pipe. We are still ignorant of the 

 chemistry of the phenomenon ; wx do not know whether the 

 drops of myelin (VircJioiv) are to be viewed as a deposit from 

 the medullary substance, or merely as a change in its mode of 

 grouping,* the observation itself being as old as Leeuwenhoeh 

 The farther progress of putrefiiction is indicated by a general 

 tumefaction of the nerve-trunk, in consequence of which the 

 individual fibres grow very dim and the neurilemma indistinct, 

 while the axis cylinder entirely disappears. Complete liquefac- 

 tion occurs at some points sooner than at others ; this gives the 

 fibres a vai'icose aj^pearance, like that presented by the fibres of 

 voluntary muscle shortly before their complete disintegration. 



§ 17. The adipose tissue plays a far more important part in 

 the course of mortification. The liquid oil readily escapes from 



* G. Walter suggests (in Virclwiv's ArcTiiv, xx. 426) that a coagulation 

 of the albuminoid substances present in the medullary sheath may cause 

 the separation of the oily matters soluble in ether, the latter uniting to 

 form globules of appreciable size. 



