CONDITIONS INFLUENCING THE TEMPERATURE. 433 



ture, one of the first points to ascertain is whether the circulation is 

 accelerated or retarded by their stimulation, or whether the respiration 

 is increased or diminished (214, II., 3), and whether the muscles of the 

 skeleton are relaxed or contracted reflexly (214, I., 3). In the former 

 case, the temperature of the interior and rectum is increased; in the 

 latter, diminished. 



That there are heat-regulating nerve-centres, has not been definitely 

 proved; with regard to the influence of vaso-motor nerves see vol. ii. 



(d) The temperature of the body rises during mental exertion. Davy 

 observed an increase of 0'3C. after vigorous mental exertion. 



Lombard observed that the temperature of the forehead rose 0'5C. during 

 mental activity and emotional disturbances. The part of the forehead corre- 

 sponded to the posterior region of both upper frontal convolutions, to the anterior 

 central convolution, and (?) to the anterior part of the posterior central convolu- 

 tion. The temperature was higher on the left side. 



(e) The parenchymatous fluids, serous fluids, and lymph produce 

 little heat owing to their feeble metabolism, hence they have the same 

 temperature as their surroundings; the epidermal and horny tissues 

 do not produce heat, they merely conduct it from subjacent structures. 



(2.) The temperature depends, to a large extent, upon the amount of 

 blood in an organ, and also upon the rapidity with which the blood is 

 renewed by the circulation. This is best observed in the difference of 

 the temperature between a cold pale bloodless hand and a warm red 

 congested one. 



Becquerel and Brechet found, that the temperature of the human biceps fell 

 several tenths of a degree, when the axillary artery was compressed. Ligature of 

 the iliac artery in a dog caused a fall of 4C. within 18 minutes; while the 

 removal of the ligature caused the temperature to rise rapidly to normal. Liga- 

 ture of the crural artery and vein in a dog causes a fall of several degrees (Landois). 

 If the extremities be kept suspended in the air, they become bloodless and cold. 



Liebermeister has pointed out a difference with regard to the external and 

 internal parts of the body. The external parts give off more heat than they 

 produce, so that they become cooler the more slowly new blood flows into them, 

 and warmer the greater the rapidity of the blood-stream through them. Accelera- 

 tion of the blood-stream, therefore, causes the temperature of peripheral parts 

 to approximate more and more to the temperature of internal organs, while 

 retardation of the blood-stream causes them to approach the temperature of the 

 surrounding medium. Exactly the reverse is the case with internal parts, where 

 a large amount of heat is produced, and heat is given up almost alone to the 

 blood which flows through them. Their temperature must fall when the blood- 

 stream through them is accelerated, and it is raised when the blood-stream is- 

 retarded (Heidenhain). Hence it follows, that the greater the difference of the 

 temperature between peripheral and internal parts, the slower must be the 

 velocity of the circulation. 



(3.) If the position of an organ be such, or if other conditions 



28 



