lowered, the peripheral pulse may be ab- sent.  The  pulse  rate  in  hemorrhagic  shock may reach 140 or higher. An exception is neurogenic shock, where the pulse rate is slowed,  often  below  60. 7. The blood pressure is usually lowered in moderately  severe  shock;  the  systolic pressure drops below 100 while the pulse rises above 100. The body is compensating for  circulatory  fluid  loss  by  peripheral vasoconstriction.  This  process  tends  to maintain the blood pressure at nearly a normal  level  despite  moderately  severe loss of circulating blood volume. A point comes,   however,   when   decompensation occurs,  and  a  small  additional  loss  will then  produce  an  alarming  and  sudden  fall in  blood  pressure. 8.  There  may  be  nausea,  vomiting,  and dryness  of  the  mouth,  lips,  and  tongue. 9.  Surface  veins  may  collapse.  Veins  nor- mally  visible  at  the  front  of  the  elbow, forearms, and the back of the hands will be  hard  to  distinguish. 10.  There  are  frequent  complaints  of  thirst. Even  the  severely  wounded  may  complain of thirst rather than pain. 11.  The  kidneys  may  shut  down.  Urine  for- mation  either  ceases  or  becomes  greatly diminished if the systolic blood pressure falls  below  80  for  long  periods  of  time. 12.  The  person  may  faint  from  inadequate venous  blood  return  to  the  heart.  This may be the result of a temporary gravita- tional   pooling   of   the   blood   associated with  standing  up  too  quickly. Hypovolemic  Shock This  condition  is  also  known  as  oligemic  or hematogenic  shock.  The  essential  feature  of  all forms of hypovolemic shock is loss of fluid from the  circulating  blood  volume,  so  that  adequate  cir- culation cannot be maintained to all parts of the body. In  cases  where  there  is  internal  or  external hemorrhage  due  to  trauma  (hemorrhagic  shock) there is a loss of whole blood, including red blood cells.  The  body  tends  to  restore  the  circulatory volume by supplying fluid from the body tissues. There is a resulting progressive fall in the hemato- crit (ratio of red blood cells to plasma) and in the red  blood  cell  count  due  to  hemodilution, However,  since  hemodilution  is  not  an  excessively rapid process, the hematocrit is a poor indicator of  acute  blood  loss,  i.e.,  less  than  24  hours  old, In burn shock, on the other hand, there is a progressively increased hematocrit and red blood cell count due to hemoconcentration from loss of the plasma fraction of the blood into and through the burned area. A  third  form  of  hypovolemic  shock  occurs  in cases  of  severe  diarrhea  and  vomiting,  where  body fluids  and  electrolytes  (sodium,  potassium,  and chloride)   are   lost.   This   also   contributes   to   a decrease  in  circulating  blood  volume. Neurogenic  Shock Neurogenic  shock,  sometimes  called  vasogenic shock,  results  from  the  disruption  of  autonomic nervous   system   control   over   vasoconstriction. Under normal conditions the autonomic nervous system keeps the muscles of the veins and arteries partially contracted. At the onset of most forms of   shock, further   constriction   is   signaled. However, the vascular muscles cannot maintain this contraction indefinitely. A number of factors, including  increased  fluid  loss,  central  nervous system trauma, or emotional shock, can override the autonomic nervous system control. The veins and  arteries  immediately  dilate,  drastically  ex- panding  the  volume  of  the  circulatory  system, with  a  corresponding  reduction  of  blood  pressure. Simple  fainting  (syncope)  is  a  variation  of neurogenic shock. It often is the result of a tempo- rary gravitational pooling of the blood as a per- son  stands  up.  As  the  person  falls,  blood  again rushes to the head, and the problem is solved. It may  also  be  induced  by  fear  or  horror,  which override  the  autonomic  nervous  system  control. Other variations of neurogenic shock that are important  to  the  corpsman  are  shell  shock  and bomb shock. These are psychological adjustment reactions  to  extremely  stressful  wartime  expe- riences  and  do  not  relate  to  the  collapse  of  the cardiovascular system. Symptoms range from in- tense   fear   to   complete   dementia   and   are manifestations of a loss of nervous control. Care is limited to emotional support and evacuation to the  care  of  a  psychiatrist  or  psychologist. Cardiogenic Shock Cardiogenic  shock  is  caused  by  inadequate functioning of the heart, not by loss of circulating blood volume. If the heart muscle is weakened by disease or damaged by trauma or lack of oxygen, as in cases of pulmonary disease, suffocation, or 4-48