Discussion 163 



the absolute volume was very low relative to that of normal infants. At 

 this time he showed an increase in all these handicaps of failing function. 



Talbot: Did he have a low absolute plasma volume? 



Young: Yes, but it was not very low per kg. /body weight. 



Talbot: That might be the answer to the problem. 



Bull: I should like to support that because we often find changed 

 plasma volumes in burns, where the situation is similar to that of ne- 

 phrosis. The extracellular fluid volume is not a good index of circulatory 

 competence ; the plasma volume can alter independently of it. 



Fejfar: The longer circulation time showed in this case would mean 

 that the cardiac output was lower, and one can say that in all circum- 

 stances where the cardiac output is inadequate, there is a decrease in 

 renal blood flow. It is not necessary for it to be connected with a decrease 

 in blood volume. 



Black: With a very high pulse rate and low cardiac output there 

 must be a fantastic decrease in stroke volume. That may be just a part 

 of the diminished blood volume, or the newborn infant may have a 

 diminished stroke volume. Perhaps the heart size is small in relation to 

 body size. 



Young : The great value of this paper is in explaining why the baby is 

 more susceptible to stress than the adult, although he appears to have 

 plenty of water. This particular way of setting out these relationships is 

 very valuable from that point of view. To some people it has always been 

 rather a puzzle that although the extracellular fluid volume is relatively 

 high, it still is not high compared with the phj^siological demands made 

 on it. 



Heller : We are always talking about the large body water content or 

 the high extracellular fluid volume in babies and young animals. Are 

 they accidental, as it were — due for instance to some prenatal endocrine 

 influences — or have they any functional significance? I have always 

 been struck by the similarity between the water metabolism of the new- 

 born animal and baby and animals with experimental nutritional oedema. 



Davson : It depends whether the large water content is necessitated by 

 the geometry of the animal. If you had a sparse number of muscle fibres, 

 then you would have a bigger extracellular space to fill out the gap. The 

 animal's extracellular geometry changes gradually and the space really 

 has no functional significance except in so far as a muscle with more 

 muscle cells in it per unit of weight is a more efficient muscle. 



Fourman : There is not a bag, to be filled either by muscle or by water. 

 Again, it all depends on the size of the cells. 



Is the extra water of the baby in the muscle, the connective tissue or 

 the skin? 



Davson : In the adult animal you can correlate the amount of collagen 

 with the amount of extracellular fluid. 



Widdoivson : Most of the extracellular fluid is in the skeletal muscle. 

 This is one of the biggest tissues of the body and it is the one which 

 changes most in composition with development. Tissues like the heart 

 and the liver change very much less in their extra- and intracellular 

 relationships with development. The heart, for example, is very much 



