TEMPERATURE OF ORGANS. 323 



therefore, when the metabolism is increased, the amount of heat produced is 

 similarly increased. 



(a) Glands produce more heat during the act of secretion, as is proved by the 

 higher temperature of their secretion, or by the higher temperature of the venous 

 blood flowing out of their veins. 



Ludvvig found that when he stimulated the chorda tympani, the saliva of the submaxillary 

 gland was 1 '5 C. warmer than the blood in the carotid, which supplied the gland with blood 

 (p. 213). The blood in the renal vein in a kidney which is secreting is warmer than the blood 

 in the renal artery. The secreting liver produces much heat ( 178). CI. Bernard investigated 

 the temperature of the blood of the portal and hepatic veins during hunger, at the beginning 

 of digestion, and when digestion was most active, and he found : 

 Temperature of portal vein, 

 ,, hepatic vein, 



Temperature of portal vein, 



,, hepatic vein, 



Temperature of portal vein, 



,, hepatic vein, 



In the dog a moderate diet, chemical or mechanical stimulation of the gastric mucous mem- 

 brane, or even the sight of food, raises the temperature in the stomach and intestine. 



(b) When the muscles contract, they evolve heat. Davy, found that an active 

 muscle became 0*7 C. warmer ; while Becquerel, by means of a thermo-galvano- 

 meter, found that human muscles, when kept contracted for five minutes, became 

 1 C. warmer ( 302). 



This is one of the reasons why the temperature may rise above 40 during rapid running. 

 A temperature obtained by energetic muscular action usually does not fall to the normal until 

 after resting for 1| hour. The low temperature of paralysed limbs depends partly upon the 

 absence of the muscular contractions. 



(c) With regard to the effect of sensory nerves upon the temperature, some of 

 the chief points to ascertain are 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, 1., 3). In the former case the temperature of the interior and rectum is in- 

 creased ; in the latter, diminished. 



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

 an increase of 0*3 C. after vigorous mental exertion. 



(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 circula- 

 tion. 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 crural artery and vein in 

 a dog causes a fall of several degrees. 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. Acceleration 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. 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. 



