DEVELOPMENT OP HEAT BT OXIDATION OF FAT. 131 



tissue. Fat is a bad conductor of heat, and many 

 animals much exposed to arctic cold are remarkable 

 for the very large quantity of adipose tissue which 

 serves as a protective covering. In hybernating 

 aninials large quantities of ad'pose tissue are found 

 just prior to the commencement of the winter sleep. 

 The fatty matter during hybernation is slowly taken 

 np by biop'asm and gradually changed, being pro- 

 bably at last got rid of as carbonic acid and water. 

 By the slow oxidation that takes place, the slight 

 amount of animal heat requLred during this period of 

 total inactivity is developed. 



184. Development of heat by oxidation of fat.— 

 It is generally supposed that the development of heat 

 is occasioned entirely by the disintegration of fat, 

 the oxygen uniting with the carbon, and a propor- 

 tionate quantity of carbonic acid being thus f jrmed. 

 But it may be fairly questioned whether the high 

 temperature of the warm-blooded animals can be at- 

 tributed solely to the combustion of fatty material, 

 seeing that in many conditions in which the tempe- 

 rature rises many degrees above the normal standard 

 within a very short period of time, the oxidising pro- 

 cess is completely at fault, and the quanity of oxygen 

 consumed is actually less than in health. The large 

 amount of fat existing in every form of nerve tissue 

 clearly indicates that the action of the nervous system 

 so essential to the maintenance of life is in some way 

 dependent upon the due supply of a suflB.cient quan- 

 titv of nutrient material containinof the elements from 

 which fat may be formed, and there can be no doubt 

 that of the fatty matter taken in the food a consider- 

 able proportion is appropriated by the bioplasm of the 

 nerve textures. 



185. The formation of adipose tissue. — The process 

 of foiTnation of adipose tissue may be well studied in 

 the embryo of any vertebrate animal. Long before 

 fat is actually produced, the embryonic matter (bio- 



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