792 



DEATH. 



to the distribution of blood throughout the 

 system, and the other parts may die from the 

 want of this supply, their mechanism remain- 

 ing entire. Or the injury, notwithstanding 

 that the part may not be thus functionally es- 

 sential to the circulation, may exert a no less 

 certain operation, either indirectly by an im- 

 pression made upon the central organs of in- 

 nervation, and reflected upon those of circu- 

 lation and respiration, or immediately by an 

 impression upon the latter. (See the remarks 

 upon Systemic Death.) The propagation 

 of the dissolution will depend much upon the 

 peculiar organization of the animal ; but in 

 all cases, as we have already intimated, text- 

 ural death in one part has no immediate in- 

 fluence in producing the same kind of death 

 in other parts ; the latter event will be found 

 attributable to the impediment offered by the 

 former to some important function of the 

 whole system. The textural lesion which we 

 have been considering may be caused either by 

 mechanical violence, or by chemical action, 

 such as that of corrosive substances and of 

 heat. It is possible that solid tissue may un- 

 dergo spontaneous decomposition, but we are 

 unable to ascertain the fact, because in ulti- 

 mate structure, where fluids and solids are so 

 intimately intermixed, we have no means of 

 distinguishing the priority of changes. 



Arrest of the fluid of nutrition. The access 

 of this fluid is variously provided for in the 

 different classes of animals. The capillary cir- 

 culation in the higher species resembles that 

 which suffices for the whole system in the 

 lower species, inasmuch as the blood in the 

 capillaries of a tissue bears the same relation 

 to that tissue, as the water in the stomach of 

 one of the Radiata to the whole animal. The 

 consequences of abstracting the fluid in the one 

 case, or of cutting off the supply of blood in 

 the other by obstructing its vessels, will be pre- 

 cisely analogous. The polype will desiccate, 

 lose its proper form, and decay; the medusa 

 will shrivel and putrefy; while in man the 

 tissue dies, and is decomposed, as in senile 

 gangrene, or in the sloughing of a haemorrhoid 

 to which a ligature has been applied. Sup- 

 pression of the action of the heart violates 

 throughout the body the condition of vitality 

 under discussion, and consequently all the 

 tissues die, but the phenomena which they 

 exhibit are not the same as in more partial 

 obstruction of the circulation, because the 

 chemical agencies are different, particularly 

 that of surrounding heat. A gangrenous spot 

 is under the influence of an atmosphere of 98 

 at the lowest; while the deader dying organs 

 of animals, which have been simultaneously 

 deprived of their circulation, are submitted 

 only to the temperature of the media in which 

 they may chance to be placed. The higher 

 this may be within certain limits, the more 

 closely will the putrefactive changes resemble 

 those of gangrene. It must be remembered, 

 however, that in the latter case other chemical 

 agents are probably presented in the fluids 

 effused by those contiguous parts which still 

 maintain their vitality. 



Dependence upon the circulation differs in 

 different animals. The heart of a salamander 

 may be excised, and yet the animal will live 

 for several hours, or even a day or two after 

 the operation ;* its possession of life being in- 

 ferred from the exhibition, not merely of cer- 

 tain organic actions, but even of those of rela- 

 tion. It is plain, then, that in animals of this 

 tribe, the brain and spinal marrow and other 

 organs do not require so constant an inter- 

 course with the blood as in certain other species ; 

 and while we know with tolerable certainty 

 that they do not need it for calorific purposes, 

 it is not improbable that their textures are less 

 frequently repaired than those of the warm- 

 blooded classes. Dr. Edwards concludes that 

 life in the above instance is maintained by the 

 organs of innervation, whose function, as we 

 have remarked, continues unimpaired. We 

 should regard the integrity of their action 

 rather as a sign than as a cause of continued 

 vitality ; other signs being perceptible in the 

 persistence of the capillary actions, for which 

 the fluids still remaining in the tissues may be 

 sufficient. 



Retention of fluid in the tissues. Removal 

 of the effete fluid is provided for in the Porifera 

 by ejects; in the Polypifera by expulsion from 

 the central cavity and by transpiration ; in the 

 Acalephse by anal apertures ; and in vascular 

 animals by vessels especially appropriated to 

 the purpose, by transpiration, and by various 

 excretions. This condition of molecular life 

 is less easily violated than those already spo- 

 ken of, because the modes of fulfilling it are 

 more numerous. This is equally true whether 

 we speak of the simple animal forms, or of the 

 tissues of the more complicated ; mortification 

 is less frequently the result of venous than of 

 arterial obstruction. Unquestionably turgescence 

 and inflammation may ensue from the former, 

 and may terminate in gangrene ; but it is far 

 more common for the part to be relieved by 

 the excretion of various fluids, constituting 

 haemorrhage and dropsy, until new channels are 

 found for the returning blood. Hence it ap- 

 pears that a redundance of fluid is less dan- 

 gerous to organic structures than a deficiency. 



Depravation of' the fluid of nutrition. It 

 is obvious that as the structures are elaborated 

 either from the blood in the higher animals, or 

 from the fluids corresponding to it in the in- 

 ferior classes, the assimilative processes must 

 be deranged and ultimately brought to a stop, 

 if the liquids are wanting in the proper mate- 

 rials. Their quality may be deteriorated in 

 various modes ; by imperfect respiration, by 

 bad or scanty alimentation, and by insufficient 

 or excessive excretion. Each of these causes 

 is traced easily enough in the degenerated tex- 

 tures of some animals, but with more difficulty 

 in the simpler classes, because the functions 

 just alluded to are not in the latter concen- 

 trated within a space that admits of analysis so 

 well as in the former. The effect of obstructed 

 aeration of the blood however is soon mani- 



* Edwards, On the Influence of Physical Agents, 

 &e. translated by Drs. Hodgkin and Fisher. 



