6 THE METHOD OF MAKING POST-MORTEM EXAMINATIONS. 



Cooling of the Body. After death the chemical changes upon which 

 the maintenance of the temperature depends rapidly diminish, and the 

 body gradually cools to the temperature of the surrounding medium. 

 This usually occurs in from about fifteen to twenty hours, but the time 

 required depends upon a variety of conditions. Immediately after death 

 there is, in nearly all cases, a slight elevation of internal temperature, 

 owing to the fact that the metabolic changes in the tissues still continue 

 for a time, while the blood ceases to be cooled by passing through the 

 lungs and peripheral capillaries. After death from certain diseases- 

 yellow fever, cholera, rheumatic fever, and tetanus a considerable ele- 

 vation of internal temperature has been repeatedly observed. The time 

 occupied by the cooling of the body may be prolonged after sudden death 

 from accidents, acute diseases, apoplexy, and asphyxia. A number of 

 cases is recorded in which the body retained its heat for several days, 

 without known cause. 



After death from wasting chronic disease, and in some cases after 

 severe haemorrhages, the cooling of the body is very rapid, the internal 

 temperature being reduced to that of the surrounding air within four or 

 five hours. Fat bodies cool less quickly than lean ones, the bodies of 

 well-nourished adults less quickly than those of children or old persons. 

 The temperature of the surrounding medium, the degree of protection of 

 the body from currents of air, of course, modify the progress of 

 cooling ; and the internal organs naturally retain their heat longer than 

 the surface of the body. The rate at which cooling occurs is most rapid, 

 as a rule, during the hours immediately following death, notwithstand- 

 ing the post-mortem rise which may ensue. 



It will thus be seen that, if required to pronounce upon the time 

 which has elapsed since death in a given case, we can do so only approxi- 

 mately. It is necessary to take into account all of the above-mentioned 

 conditions which modify the rate of cooling of the body, and then we 

 may be able to state only the probabilities of the case. It is furthermore 

 unsafe in any case to infer the cause of death from the rate of cooling of 

 the body. 



Rigor Mortis. Death is usually succeeded immediately by a period of 

 complete muscular relaxation. The jaw drops and the limbs become 

 flaccid. The muscles may retain for two or three hours, however, the 

 capacity of contracting, on the application of appropriate stimuli. Oil 

 the average, within six hours the muscles become firm and rigid. This 

 post-mortem rigidity is called rigor mortis. On the occurrence of the 

 rigor mortis the muscles become fixed in whatever position they may 

 have had at the time of its occurrence. It usually begins in the muscles 

 of the eyelids, extends to those of the back of the neck and lower jaw, 

 then to the face and neck, and thence passing downward affects the mus- 

 cles of the thorax and lower extremities. It usually disappears in the 

 same order. Although commencing on the average six hours after death, 

 it may set in at once or be delayed for twenty-four hours or more. It 



