25J 



and the death of the independent functions may succeed to this 

 condition of the blood-vessels. Whether life ceases wholly in this 

 instance from disorder of the circulation, or whether a change which 

 is directly propagated from the place of the injury, to parts other- 

 wise not related, can scarcely be decided ; at least, the precise share 

 of each of these modes of impairing function or destroying life 

 cannot be defined. By these modes aud their complication, functions 

 are modified or destroyed where the relation of regular dependence 

 does not subsist. 



21. The ways in which the effects of causes are extended be* 

 yond the primary seat of their operation appear simple; they are 

 reduced to two, the direct and the mediate ; but their complexity 

 may be greatly increased. As the direct and the indirect might be 

 mixed, or the direct may have complex relations, as when functions 

 cease in a third, by the relation which a primary, has with a 

 secondary seat; or a complication might grow out of the relations 

 between the direct and the indirect modes of influence in different 

 seats; their connexion may be extensive or partial, common or par- 

 ticular; or obtaining in some seats and not in others: these varieties 

 all tend to modify phenomena. Such a tissue of subordination and 

 re-agency can be unravelled only by specific investigation, which 

 must respect some or other of the numerous examples in which it is 

 displayed. 



22. It has been attempted to establish dependence by injury : 

 this mode of experimenting has, in some of our former pages, been 

 rejected, and the grounds of the rejection are there stated. I have 

 only further to remark upon this subject, that when muscular motion 

 is for a few minutes exhibited in dependent seats, under the infliction 

 of an injury which destroys the source of their properties, this hap- 

 pens, not by an assimilation of functional properties in the dependent 

 seat, but by a progressive disorder of their source; the injury of 

 which, though speedily, is not immediately fatal. Thus, an animal 

 will use for a time vehemently the voluntary muscles, after his head 

 is cut oft": the reason is, that the spinal marrow is capable of sup- 

 plying properties for muscular motion, until life is destroyed 

 mediately, as in this case, by the prevention of respiration, or an 

 influence connected with the blood. This circumstance indicates 

 that the voluntary powers of the muscles supplied by spinal nerves 

 is not dependent upon the continuity of the spinal marrow with the 

 brain ; at the same time it must be remarked, that a different con- 

 elusion is indicated by the paralysis of the lower extremities, which 

 is known to succeed certain injuries of the medulla spinalis about 

 the lumbar, or even the dorsal, vertebrae. We find it agreeable 

 with our experience in other respects, that when properties of 

 motion are no longer communicated to the muscles from a true r 

 unequivocal source, the powers of motion cease immediately and 

 entirely in the dependent seat; just as a leg drops, aud is not con- 

 vulsed, the moment that aw axillary plexus is divided with one 

 stroke of the bistoury. . . . . 



w M 



