CHAPTER XXIV. 



ANIMAL HEAT. 



1. ^Calorification, is a function of animal bodies, not yet 

 thoroughly understood.) We see certain phenomena, but the 

 causes are hidden from our view. It is very doubtful wheth- 

 er we shall ever be able to penetrate the veil which con- 

 ceals the wonderful operations of vital chemistry ; and per- 

 haps it would lead to no useful result if we could ; should 

 we ever attain to the knowledge of all the natural laws of 

 life, we shall then be assured that it is only in consequence 

 of their violation that man pays, by suffering, sickness and 

 premature death, the penalty of their transgression. 



2. What causes the temperature of the body to be main- 

 tained at an average of ninety -eight degrees, and this, too, 

 under all climates, and at all seasons ? \In the first place, 

 respiration is much concerned in the production of animal 

 heat.) It was once indeed believed, that the chief office of 

 respiration was to cool the blood ; and that the heart was the 

 great furnace of the system, where all the heat was pro- 

 duced. 



3. (When it was discovered that both in combustion and 

 respiration, carbonic acid was produced, and oxygen ab- 

 sorbed, it was at once surmised, that breathing must be a kind 

 of combustion by which all the heat of the body is generat- 

 ed.^ But it was objected to this, (that if the heat was all pro- 

 duced in the lungs, why were not the lungs hotter than the 

 other parts of the body^)as those parts of a stove in contact 

 with the fuel, are hotter than those at a distance. 



4. This objection to Mr. Black's hypothesis, led Mr. 

 Crawford to propose the following solution. Although ani- 

 mal heat is produced in the lungs by the process of respira- 

 tion, yet as arterial blood has a greater capacity for caloric 



