GENERAL METABOLISM 



[PT. Ill 



had 82-8 per cent, and the cord 79-0 per cent., while Donaldson 

 found for Rana adult brain 84-9 per cent, and cord 80-5 per cent. 

 Rosenheim, on the other hand, found in human brain 90-29 per cent, 

 for the 36 weeks' foetus and 85-8 per cent, for the infant shortly 

 after birth, and a trend in the same direction was found by Gundobin 

 and by Koch, who obtained the following figures : 



Brain of foetus of pig 50 mm. long 

 Brain of foetus of pig 100 mm. long 

 Brain of newly-born albino rat ... 

 Brain of adult albino rat 



0/ 

 /o 



90-78 



91-01 



89-58 



78-10 



It is safe to say, then, that, though in certain cases the water- 

 content of embryonic tissues seems to remain unchanged with age, 

 there are a few instances of a 

 rise, and the majority of experi- 

 ments show that it falls. The ex- 

 planation of this fall is difficult, 

 though, as we have observed, 

 some investigators have seen in 

 it perhaps the most fundamental 

 attribute of the ageing-process. 

 A point which does not seem 

 to have been noticed so far is 

 that the high water-content in 

 the early stages may be related 

 to the importance of primitive 

 connective tissue and its con- 

 tained lymph. I have already 

 drawn attention to the primi- 

 tive undifferentiated connective 

 tissue, first discovered by von 



Szily, in connection with the initially high concentration of glucose 

 in combination with protein^, and it will again be mentioned in 

 connection with the relatively high silicon content of young em- 

 bryos. But what is important here is the fact that connective tissue 

 has always a high water-content, and this might explain the pheno- 

 menon now under discussion. Thus Skelton found that bleeding in 

 mammals produced a flow of water from the tissues into the blood, 

 and by appropriate experiments he was able to ascertain what per- 



^ See p. 566. 



o Cowmuscle(jacubovitsch) 

 ® Pig brain (Mendel S^ Leavenworth) 

 © Pig liver ( " " " ) 



o Sheep lung(Faure-Fremieb«tDragoiu) 



• Cow brain (Schlossberger) 

 ' ■ " heart ( 



♦ " lungs ( 

 A " muscle! 

 ▼ » liver ( 

 © " blood ( 



Cow length in cms. 



■^ 



Cow&,Sheep .5 weeks 

 Pig mm. 50 



10 

 100 



15 

 150 



20 

 200 



Fig. 231 



