CONCUSSION. 115 



paralyzed, and cannot expel the urine, -which sometimes dribbles 

 off in small quantities. This indicates a state of great disten- 

 sion of the bladder, and that the urine forces its neck to such an 

 extent as to allow the overflow of its contents. 



Some cases are characterised by convidsive twitchings, rapid, 

 feeble pulse, and hurried respiration — symptoms believed to 

 denote wound of the brain rather than concussion. 



It has been discovered by dissections that haemorrhage from 

 concussion may occur in any of the five following situations : — 

 l5^. Between the cranium and dura mater ; 2d. Under the dura 

 mater into the cavity of the tunica arachnoidea ; Zd. Between the 

 tunica arachnoidea and pia mater ; Ath. Between the pia mater 

 and brain ; and 5th. Into the substance of the brain itself. 



The method of trephining for injuries of the cranium is de- 

 scribed as follows by the great surgeon Syme : — " If the bone 

 be not sufficiently exposed by the original injury, a crucial or 

 triangular incision must be made through the scalp, the flaps 

 of which are to be dissected back. The pericranium is next 

 scraped off sufficiently to prevent it from impeding the teeth of 

 the saw, which is applied at first with its centre pin, to keep it 

 steady, and afterwards, when a groove has been formed, this 

 obstacle to its progress is removed. The sawing must be con- 

 ducted cautiously, as the skull is not always equally thick, 

 and is often throughout very thin, with hardly any percaptible 

 diploe. A toothpick or probe should be introduced from time 

 to time, to ascertain whether or not the bone be perforated at 

 any part of the circle, and when the whole seems to be nearly 

 cut through, an elevator or forceps may be employed to raise the 

 detached piece. If circumstances appear to require the removal 

 of more bone, the same means are to be repeated, or the process 

 may be accelerated, if the portion be extensive, by Hey's saw, 

 as it is usually called, which proves convenient for connecting 

 the circular apertures together, so as to separate at once a 

 large portion of cranium. After the operation the woimd is 

 to be lightly dressed, and the general treatment conducted with 

 the view of checking any tendency to inflammatory action." 



After the operation, well-regulated pressure should be applied 

 to the part by means of pads of tow and bandages ; if this is 

 not done, a tumour is apt to make its appearance, which consists 

 of a protrusion of the brain, and is termed— 



