772 THE RESPIRATION AND [pt. hi 



(see also Superbi) . Thus Hammond who implanted foetal tissues into 

 the uterine wall, found that they possessed no power of establishing 

 themselves there, unlike the foetal trophoblast. The uterine grafts 

 were absorbed. 



Summarising, we may say that four main types of respiratory 

 metabolism have been revealed by the studies initiated by Warburg : 



(a) Normal resting tissue — anaerobic glycolysis slight, aerobic 

 glycolysis absent, respiratory rate generally rather high, U. negative, 

 Warburg quotient ^ 0-3. 



{b) Normal growing tissue [embryonic) — anaerobic glycolysis high, 

 aerobic glycolysis very slight or absent, respiratory rate high, 

 U. negative, Warburg quotient ^ 0-3, 



[c) Abnormal growing tissue {malign neoplasms) — aerobic and anaero- 

 bic glycolysis both high, respiratory rate usually low, U. positive, 

 Warburg quotient > 2-0. 



[d) Abnormal growing tissue {benign neoplasms) — all factors generally 

 rather low, U. positive, Warburg quotient 0-5-1 -3. 



Completer details are to be found in the reviews of Warburg & 

 Minami ; Warburg, Negelein & Posener ; Cramer ; Cannan ; and 

 particularly Warburg. 



4-21. The Genesis of Heat regulation 



The only other subject which calls for consideration in this chapter 

 is that of the ontogeny of heat regulation. It has been known for 

 a long time that, just as animals which are normally homoiosmotic 

 are yet poikilosmotic while in their embryonic state, so the capacity 

 of heat regulation possessed by homoiothermic organisms arises at 

 a definite moment in the individual life-cycle. 



Edwards, who worked about the year 1820, was the first to notice 

 this. He found that the temperature of newly born puppies, kittens, 

 and rabbits fell when the animal was removed from its warm sur- 

 roundings, and continued to fall until it almost reached the tempera- 

 ture of the air. Guinea-pigs, on the other hand, were able to 

 maintain their temperature very well immediately after birth. 

 Edwards divided homoiothermic animals into two classes, {a) those 

 which are at birth bhnd, helpless, naked, and poikilothermic, and 

 {b) those with open eyes, skin covered with hair or feathers, and 

 homoiothermic. This classification corresponds exactly with nidi- 

 fugous and nidicolous birds (see pp. 272 and 317). In the case of 



