MECHANISM OF THE PRODUCTION OF ANIMAL HEAT 403 



or of a nerve-centre, capable of influencing the general process of calori- 

 fication. Experiments have been made, chiefly on parts of the en- 

 cephalon, with the view of determining the existence and location of 

 heat-centres. Ott describes four heat-centres, irritation of which 

 by puncture increases the temperature of the body in rabbits by several 

 degrees (4 to 6 Fahr., or 2.2 to 3.3 C). These four centres are the 

 following: I, in front of and beneath the corpus striatum (Ott); 2, the 

 median portion of the corpora striata and the subjacent parts (Aronsohn 

 and Sachs); 3, between the corpus striatum and the optic thalamus 

 (Ott) ; 4, the anterior inner end of the optic thalamus (Ott). Puncture 

 of these parts is followed by rise in temperature, which continues for a 

 variable time two to four days. A similar centre has been described 

 as existing in the dog in the cortex of the anterior portion of the upper 

 surface of the brain near the median line (Eulenberg and Landois). 

 The conductors connected with these centres decussate arid pass through 

 the bulb and the spinal cord. The effects of puncture or stimulation of 

 these parts probably is inhibitory. 



MECHANISM OF THE PRODUCTION OF ANIMAL HEAT 



In man and in the warm-blooded animals generally, the maintenance 

 of the temperature of the organism at a nearly fixed standard is a neces- 

 sity of life ; and while heat is generated with an activity that is con- 

 stantly varying, it is counterbalanced by physiological loss of heat from 

 the cutaneous and respiratory surfaces. Variations in the activity of 

 calorification are not to be measured by corresponding changes in the 

 body-temperature, but are to be estimated by calculating the quantity of 

 heat lost. The ability of the human race to live in all climates is 

 explained by the adaptability of man to different conditions of diet and 

 exercise and by the power of regulating loss of heat from the surface 

 by appropriate clothing. 



So far as it is possible to determine by experiment, not only is there 

 no particular part or organ in the body endowed with the special office 

 of calorification, but every part in which the nutritive forces are in 

 operation produces a certain quantity of heat ; and this probably is true 

 of the blood-corpuscles and other anatomical elements of this class. 

 The production of heat in the body is general and is one of the neces- 

 sary results of the process of nutrition ; but, with nutrition, it is subject 

 to local variations, as is illustrated in the effects of operations on the 

 vasomotor nerves and in the phenomena of inflammation. 



In 1866 Frankland made a number of calculations of the heat-units 

 and the estimated force-value of various articles of food, which are now 



