SOURCES OF ASTMAL HEAT. 421 



deuce to show that the lungs are special organs of calorifi- 

 cation ; and any generation of heat that takes place here is 

 due, probably, to purely physical phenomena in the blood. 



The theory that all the respiratory changes, involving 

 the consumption of oxygen, the production of carbonic acid, 

 and the evolution of heat, take place in the blood as it cir- 

 culates, was advanced many years ago by Lagrange and 

 Hassenfratz ; 1 but recent investigations, showing the ap- 

 propriation of oxygen and the evolution of carbonic acid by 

 the tissues deprived of blood, and the evident production of 

 heat in the muscular substance and in other parts, have 

 completely overthrown this hypothesis. 



It is only necessary to refer back to the pages treating 

 of the variations in the temperature of the blood in different 

 parts, to show that heat is produced in the general system, 

 and not in any particular organ, or in the blood as it circu- 

 lates. The experiments of Matteucci, showing an elevation 

 of temperature in a muscle excited to contraction after it 

 had been removed from the body, and the observations of 

 Becquerel and Breschet, showing increased development of 

 heat by muscular contraction, are sufficient evidence of the 

 production of heat in the muscular system ; 2 and, inasmuch 

 as this constitutes by far the greatest part of the weight of 

 the body, it is a most important source of animal heat. 



It has been demonstrated, by the experiments of Bernard, 

 that the blood becomes notably warmer in passing through 

 the abdominal viscera. This is particularly marked in the 

 liver, and it shows that the large and highly-organized vis- 

 cera are also important sources of caloric. 3 



As far as it is possible to determine by experimental 

 demonstration, not only is there no particular part or organ 



1 HASSENFRATZ, Memoire sur la combination de Foxygene avec le carlone et Vhy- 

 drogene du sang, mr la dissolution de I'oxygene dans le sang, et sur la maniere dont 

 le calorique se dfyage. Annales de chimie, Paris, 1791, tome ix., p. 261. 



2 See page 414. 



3 See page 399. 



