39 HEAT-CONDUCTION OF ANIMAL TISSUES. 



hours. Senator found that a dog weighing 6330 grams produced 15,370 calories, 

 with a loss of 3.67 grams of carbon dioxid. 



An adult man produces at rest in twenty-four hours 2,400,000 

 calories, therefore 100,000 in an hour. One kilogram of body-weight 

 produces in twenty-four hours approximately 34,000 calories, therefore 

 1417 in an hour. These figures increase with increase in the total 

 metabolism and also with functional activity. 



The first calorimetric observations on man were made by Scharling in 1849. 

 Leyden introduced the leg alone into the chamber of the calorimeter. This raised 

 the temperature of 6600 grams of water i C. in an hour. If it be assumed that 

 the total superficies of the body is about fifteen times as great as that of the leg 

 the human body, assuming equal loss, would produce 2,376,000 calories in twenty- 

 four hours. 



HEAT-CONDUCTION OF ANIMAL TISSUES. 

 EXPANSIBILITY OF ANIMAL TISSUES BY HEAT. 



The heat-conduction of animal tissues is principally of importance 

 in relation to the arrangement of the external integument and the sub- 

 cutaneous fatty tissue. The latter especially serves as a protecting 

 shield in warm-blooded animals living in cold water (whale, walrus, seal) 

 and through this abstraction of heat by means of conduction from the 

 interior of the body is practically impossible. Few investigations have 

 been made upon this question. Greiss in 1870 determined the con- 

 ductivity of the following tissues by noting the distance from a central 

 source of heat introduced into the tissues at which was melted a layer 

 of wax. He studied the stomach of sheep, the bladder of oxen, the 

 skin of cattle, calves' feet, the hoofs of oxen, the bones of oxen, 

 the horns of buffaloes, the antlers of deer, ivory, mother of pearl and 

 haliotis-shell (sea-snail). He found that fibrous tissues conduct 

 better in the direction of their fibers than at right angles to their 

 course. The figures formed by the melting wax upon tissues spread 

 out over a wide area were therefore generally elliptical. Landois has 

 made observations upon a number of human tissues by determining the 

 melting-distance of a layer of paraffin from a thin test-tube filled con- 

 stantly with boiling water and applied intimately to tissues in layers 

 of equal thickness, and subsequently applied on the flat and supported 

 by threads. Desiccation was avoided, and also the effect of radiant heat. 

 Landois was able to confirm the fact of the better conduction in the 

 direction of the fibers. Next to bone the best conductor was found to be 

 blood-clot; then there followed successively spleen, liver, cartilage, ten- 

 don, muscle, elastic tissue, nails and hair, anemic skin, gastric mucous 

 membrane, washed fibrin-fibers. The great thermic conductivity of 

 the blood as compared with the much lower conductivity of bloodless 

 skin is of particular interest. In this way is explained the fact that but 

 little heat is dissipated by anemic skin, while hyperemic skin conducts 

 and gives off a much larger amount of heat. 



Like all bodies the human body undergoes expansion at elevated 

 temperatures. A man, weighing 60 kilos, will expand about 62 cu. cm. 

 with an increase of his bodily temperature from 37 C. to 40 C. Of 

 the different tissues, connective tissue (tendon) is expanded by heat, 

 while elastic tissue and skin are contracted like rubber. 



