ii THE THEKMIC ECONOMY OF THE ORGANISM 53 



Frankland (1866) was the first to investigate the heat value 

 of certain organic compounds ; Stohinann (1877) extended his 

 researches to the most important foods and constituents of the 

 body; and Eubner (1885) and Berthelot (1889) worked along 

 the same lines, carrying out the calorimetric estimations with 

 much more perfect apparatus. Still more recently (1890-91-92) 

 Stohmann, with the help of Langbein, made a careful revision of 

 the results he had already obtained, and added largely thereto. 



The Calorimetric Botrib. This method, which was introduced by 

 Berthelot, enables us to determine exactly the heat of combustion 

 of a large number of organic compounds. The apparatus (Fig. 5) 



Fio. 5. Berthelot's calorimetric bomb. 



consists of a steel vessel capable of resisting pressures of 200-300 

 atmospheres, the inner surface being covered with a special 

 enamel which is not affected by either acids or damp oxygen. 

 The cover is furnished with a central tube R, which connects the 

 interior of the vessel with a receptacle containing compressed 

 oxygen, and with a lateral tube E, which is hermetically closed 

 by a small ivory cylinder, through which passes a platinum wire 

 for conducting the electric current to the spiral wire / ; when the 

 spiral becomes incandescent, the substance under examination 

 placed in the small capsule ce attached to the lower end of the 

 support S is burnt. 



The calorimetric estimation is made in the following way : a 

 given quantity of the substance is placed in the capsule ce, the 

 spiral wire / is brought into direct contact with it, the bomb is 



